In general you are right, though in this case he missed an pure 8 ply combination. I believe it was a Horizon problem. He didn't scan the whole 8 play depth and missed this variation.
It is to me not a pure endgame mistake which you typically recognise in an voluntary piece exchange into a lost endgame.
An 8 bit program at no more then 4Mhz typically considers 7 up to 8 ply. The progam uses the shannon A Strategy, meaning he will calculate the whole tree.
This is also a reason why I have such a bad score against the Turbostar (5 to 10%) . I believe the Turbostar 432 KSO has a B-strategy program and is a real frustration for me. It scans the tree for a few ply (3 to 4) and then makes a few deep dive considerations on the most promising variations like humans do.

https://chessprogramming.wikispaces.com/Type+A+Strategy
https://chessprogramming.wikispaces.com/Type+B+Strategy