I have been into computer chess for many years and I was fully expecting those concessionary statements. I have seen enough programs in this lucrative genre where a lot of attention can be gained by fraudulently claiming you implemented chess in a seemingly impossibly small size. When confronted, the charlatans will often claim senselessly that those omissions were in fact superfluous. This is a behaviour I have unfortunately also observed in other areas of computing.

If anyone reading this is interested in small and efficient chess programs that are still reasonably strong, there was a x86 assembly port of Stockfish called asmFish from a couple of years ago (the Win64 release binary was about 130KiB). Also see OliThink (~1000 LOC) and Xiphos which has some of the simplest C code for an engine of its strength that I have seen. I have not investigated the supposedly 4K sized engines that participated in TCEC too closely but from what I have seen so far it would seem that there are a few asterisks to be attached to those claims.