Actually, Geoffrey is one of the three players in history of English Cricket to average higher than Joe Root against spin, the other two are Sir Walter Hammond and Ken Barrington, this also claims that Root averages over 65 against spin bowling!
CricViz Analysts Ben Jones & Freddie Wilde examine what makes Joe Root one of the modern game’s best players of spin.
cricviz.com
only a very small 19% of Geoffrey's dismissals come against spin bowling, for the likes of Sehwag it's 24%, 22% for Lara and 31% for Sachin and so forth.
I generally do think Geoffrey is criminally underrated as a Red Ball Batsman and there's not much between him and Chappell, still think he's a bit off that tier in general due to his tendency to let bad balls go, which even Hutton said was ridiculous. His RPI is also a little low due to his early career and final years, not that it is a very big issue for the elite openers but still.