Really?

<one factor in Karpov's favour in Linares 1994 was that he played his opponents (with the obvious exception of Kasparov) the round after they had encountered Kasparov.>

13... Bxa3 has a negative: it develops
white's rook 'for free'. Normally,
you have to move your own pieces to develop them, e.g. 1. Nf3. Not in this case: Karpov would be thoughtfully developing white's queen's rook for him. The a1 rook is now nicely placed on a1, pressuring a5.

Unless he admitted to it, I wouldn't be sure. Certainly makes sense to avoid such lines against Kasparov.

I am not sure, my feeling says to me that Black needs just two or three careful moves, then it will be over. In the final position after 20.Ng5, if Black manages to bring either the bishop (with c8-d7-c6-d5) or the a8 knight (via c7-d5) to d5 then IMO his position is won. Something else to note, the knight on e5 is pinned because of ... Qxh2+. These are just general thinking about the position there are no concrete calculations involved.

21 ... Bd7 22 Ngxf7 Rh4 23 g3 Re4 24 Ng5 Qd6 25 Nxe4 Nxe4 26 Nxd7 Qxd7 27 Qxb3 Nd6 28 Re1 Nc7 29 d5 Kf7 30 dxe6 Nxe6 31 Qf3 Kg6 32 Qd5 Nc7 33 Qd4 (eval: +0.41)

This statement is so divorced from reality that it is astonishing someone would actually put such a ridiculous thought to text.

See Karpov vs Topalov, 1994 (3 rook sacrifices!) and Karpov vs Sax, 1983 for starters, two Chess Informant Best Game Prize winners that reveal Karpov's profound tactical mastery.

Karpov-Hort 1971
Karpov-Spassky 1974 (game 9)
Karpov-Korchnoi 1974 (game 2)
Karpov-Velimirovic 1976
Tatai-Karpov 1977
Karpov-Korchnoi 1978 (8)
Timman-Karpov 1979 (Montreal)
Karpov-Hubner 1980

Another <shach matov>; this poster knows better than these great players what their very thoughts are....

<.....Incidentally, one factor in Karpov's favour in Linares 1994 was that he played his opponents (with the obvious exception of Kasparov) the round after they had encountered Kasparov.>

In <Kasparov vs Karpov 1988-2009>, Garry notes:

<13...a4?! The fruit of nearly half an hour's thought. 'Ivanchuk, who was playing close by, immediately saw with his "peripheral vision" the incredible resource 13...Bxa3!?. This spectacular stroke made such a strong impression on the journalists, that many of them reported that "already in the opening Karpov missed an opportunity to the win the game". But when a few hours later the reply 14.Bxh6! had been thoroughly studied, it transpired that its consequences were altogether unclear.' (Makarychev)

[...]

Curiously, at the board I altogether overlooked 13...Bxa3. It would appear that Karpov also did not notice it. When immediately after the game we were shown it by Ljubojevic, for both of us it was a revelation. This amazing mutual oversight, like our other mistakes, is a clear indication of the colossal nervous tension that accompanied this game.>

<For this gem, the <Weapon of Mass Destruction> cannot even claim originality, as <Eric Schiller> attempted to explain away Karpov's success thus in his book on Kasparov.>

In a <New In Chess> interview with Dirk Jan ten Geuzendam, immediately after his victory in Linares in 1994, Karpov said: <I was looking at the list and immediately saw the good news that I would get Kasparov's opponents one round later. This is good, because he gives them a hard time (laughs). And then the next day I play against them. Of course, Shirov was in the best position in this tournament. He met players who had just played Kasparov and me. Actually he proved how good this position was.>