As always GA to the rescue 
You would think so but this argument actually does not apply in Tendulkar’s case
Tendulkar in India: ave 55.48 in 59 Tests; Runs 5603, 100s (18)
Tendulkar in Pakistan: ave 40.25 in 10 Tests; Runs 483, 100s (1)
Tendulkar in SLA: ave 63.75 in 9 Tests; Runs 765, 100s (4)
Tendulkar in Bangladesh: ave 139.00 in 5 Tests; Runs 556, 100s (4)
His record in Pakistan is poor if anything, a tribute to our bowlers
If you combine all 4 stats.
Tendulkar in Subcontinent: M 83, Runs 7407, Ave. 57.42 , 100s (27)
Tendulkar outside S/C: M 73, Runs 5017, Ave. 50.68, 100s (14)
So his batting average drops by almost 7 outside sub-continent but still pretty good I w’d say. The Indian pitches seem to boost his 100s column though, a hundred roughly every third game.