Huebner vs. Portisch (1986) - why does it make sense to move h2h3 on move 9 but not 8?

I'm going through Chess: The Art of Logical Thinking, and this is the second game reviewed. The author discusses how 9. h3 is necessary to prevent black's pining of the f3 knight. However, it's not mentioned why white is not worried enough about the pin to then play 8. h3 instead, given that the bishop has the option then as well.  What does black's castling change about the situation?

I should add - the engine agrees with 8. c3 O-O 9. h3. 

I don't think it really matters whether you play h3 on move 8 or 9.

Oh it matters! On 8.h3 Black can play 8,,,Na5 exchanging off white’s bishop

Also, after white plays c3 on move 8, Bg4 is ineffective. The pin threatens nothing! White plays d3 and the bishop is misplaced on g4. After 8.c3, White wants to play d4 next. But 9.d4 Bg4 allows Black to put a lot of pressure on the White d-pawn. So that's why White plays 8.c3 (which allows White to preserve his bishop), and 9.h3 (to allow 10.d4)