The reason I don't have Javed as high as many is because he could not be given out LBW for years at home, almost all of his LBW decisions at home are in the second halve of his career. Even those, mostly in inconsequential games with Sri Lanka (1980s) and Zimbabwe, almost never given leg before wicket against good teams. Away from home, 26% of his dismissals are LBW, at home that number shrinks to 10%, and until 1985, he was given LBW for 30% of his dismissals away from home while being given LBW at home 0 times. That is a net boost of 20% less dismissals at home and that's a direct 20 or so percent inflation for his home numbers. Average is runs/dismissals so numbers of dismissals is inversely proportional to average and the fact that Javed couldn't be dismissed by LBW on turners means a lot. He could do padding and it won't mean anything, and I doubt he was generally given even nicks to the slips or keepers.
His away numbers aren't great either, never got a century in Asia outside Pakistan, average in West Indies and Australia, good on flat wickets in England but completely tanked on spicier English wickets, really only amazing on Kiwi wickets. I do think his average is a good 4-5 points inflated from his quality, due to home umpiring, some lottery wickets in England and constant games with home advantage against absolutely hopeless Indian attacks.
In England, he made 2 hundreds but the scorelines read 708-234-315/4 and 446/4 dec-459/7 dec, absolute and utter roads and both ended in draws naturally. On English wickets that produced results, he managed to do nothing and average a mere 22, on general spicier English wickets his average is even lower. In Australia, he made one good hundred at the WACA though Lillee and Thomson missed that game, his other hundred game on a road where the scorelines read 465-604-310/7 draw, and he came to bat at 306-2. In West Indies, he made a good hundred against Marshall, a decent one against Walsh + an inexperienced attack and did not manage to cross 43 runs in any other inning, averaged 33 in the West Indies.
His record in New Zealand is extremely appealing to the eye but reading into it, his 271 came in a dead draw on a wicket where Stephen Pocock and Ewan Chatfield bowled more than Richard Hadlee, because Hadlee had issues with his achillies tendon and ended up retiring hurt. Wicket was grassless and did not break up, the second game was played on "and on another perfect pitch there, a draw was the only realistic result." and so forth, once again, showing how contextually it wasn't like he bashed a Kiwi pace attack on a greentop. He is certainly one of the greatest tourists of New Zealand, but it doesn't make up for everything else.
personal opinion is if someone gives a Batsman like Kenny Barrington or Rahul Dravid, Miandad's home games then I think they'd probably average in the excess of 60, perhaps 65, helpless indian bowling on the flattest pitches ever with extra biased umpiring? at that point, it's just a matter of cashing in. It's luck that 25% of his home games come against India in historically flat conditions with umpiring bias boosted by nationslistic tendencies, never had to face Prime Hadlee at home though I think he'd have done well, getting second string New Zealand is still a boon. never had to face Lillee at home on a good wicket, only on historically flat ones with umpires not even hiding bias. Its a very generous home schedule for sure, further boosted by umpiring.
in a comparison with Gower, Gower achieved far more in Australia and the West Indies, and he had an absolute banger of a series in Pakistan on turners while I can't say the same for Javed in England on greentops. In Asia minus Pakistan, they performed similarly. Gower didn't get a series in New Zealand though did perform very well against Hadlee on green wickets at home. Generally, I don't think Gower was a match for Javed's ruthless ability to cash in, I don't think he'd average 90+ against India even with biased umpiring and on roads, but I think their abilities against good bowling is probably about the same level.
I know the issue with umpiring wasn't just Pakistan specific, but in comparison to his contemporaries statistically, people like Gavaskar/Richards have better away records than home records, people like Gower have a better away record too though England and South Africa have the lowest margin of LBW problem. Someone like Crowe was also ATG away from home after 1985/terrible early career. Boycott also had a relative away record in comparison to home record, Amarnath a way better away record and so forth.
Bluntly speaking, when you're cheating so blatantly and have such a big advantage at home of not being dismissed by LBW or knicks to the keeper, then rightfully I've to judge you primarily off your away record and Under that, I won't place Javed in the Gavaskar or Border tier, his away record is below Gower and on par with Crowe imo.