I feel like the prospect that May "bashed" New Zealand is a bit overplayed, the 1958 Kiwi attack was definitely international level with MacGibbon/Reid/Alabaster/Cave and they were playing on some extremely wet wickets, the first match was low scoring and other than May and Cowdrey, no English Batsmen managed to cross 20 runs and the team made 221 runs in total. In the third test it rained for two days straight and wicket was unplayable and May dominated and made a hundred, only the fourth test hundred could be called a poor one but still, the bowling attack wasn't terrible and the first two knocks came on a wet and then a drenched wicket, it should count for something. I feel like it was the Kiwi batting of this era that was completely pitful.
I'd say their bowling attack for 1958 is a tier above actual minnows like 2000s Bangladesh and Zimbabwe, MacGibbon and Reid are genuinely good bowlers, Alabaster was also pretty decent for a SENA spinner and Cave in context of his achievements in the unofficial tests against Australia wasn't bad either. The runs are probably no easier than some of Windies/Indian runs of the same time.
His hundred in New Zealand, well, the attack was very bad and it could be qualified as minnow bashing, I wouldn't bother doing it though, from what I can say it was a well rated hundred in some extremely windy/swingy conditions.