Know your (endgame) draws

The diagrammed position was mentioned to me by GM Nigel Short in the context of how strong GM's play open swiss events. I offered the opinion that given the variable strength of the opposition, it should generally be a matter of playing comfortable openings, and rely on technique to bring home the point. While he basically agreed with me, he did say that it wasn't just his technique that was important.
The position came from his round 8 game in the 2012 Bangkok Open. Needing to win the stay in first place he reached this ending against GM Farrukh Amonatov. In similar positions the basic idea for Black is to place the king on g7 and at the right moment bring the rook to f3 so it can then keep checking the White king from the side. However it turns out this was not one of those positions. Instead this position is already drawn, as long as Black can find the *only* move in the position. After 69.a6 the only move is 69. ... Rd5! (according to Tablebase. I did not work this one out myself). Instead Black tried the familiar approach of 69.Ra5 and after that Short found every winning move in the position.
I do feel sorry for Black, especially as any ending of this type that I would be involved it would be a cavalcade of errors. He did at least try and play the position according to the right plan, it just turned out that this was one of those positions where the general plan failed. But of course this is one of the differences between being a GM, and being a 2700 rated GM. Having the correct technique, but knowing when it isn't correct.