I can't and don't want to force anyone to stand inside my shoes, as they say. You'll see and understand what you see, from your standing.
No. Not saying that. Literal/metaphorical is a reference to how people interpret and I can't account for the multiple interpretations people are going to find. My rule is usually, unless it's Bob, to err on the side of benign interpretation, and look for meaning. But each to his own.
So let me guess: are you saying that there's literal bugs and metaphorical bugs, all the Stockfish bugs are literal, so it's metaphorically bug-free? Because that's my best guess.
Sidedness because you and the other freakily hostile guy who signed up two months ago are on a sided-dynamic, which no doubt is something to do with social "group" psychology and so on. Don't mind me, I'm used to it and it's quite interesting to watch.
(and no, I'm not going to pretend that Dann Corbit is on your side and that you're saying what he's saying. You said with enough effort you can get bug-free software, he said "If your code base has half a million lines in it, there will definitely be bugs", which contradicts your statement, so he's on my side)
There is an exponential size problem with bugs; I used to oversee QC way back, the system was bugs reported to testing, testing works out how to re-create, reports to programmer, programmer fixes it. All is spreadsheeted. Okay, so you get to situation of 200 bugs. 199 have been fixed and tested fixed. #200 gets fixed, but this involved not just testing #200, testers have to go back and test 1-199 all over again because bug fixes have an annoying tendency to recreate past bugs. Obviously this testing method has an explosive growth problem with N. It can be managed with compartmentalising, but is a problem. Some projects just get out of all control. Chess engines need not be in that class. Chess engines are not one page written in BASIC either, and clearly, amateur engine programmers, or programmers scraping some kind of living, can't afford the infrastructure needed at this level, either in their own time, or by buying it in, and it requires separate dedicated teams and they don't really have an incentive to high QC, just one that's "good enough", for them basically. But, if you have the infrastructure to test, and the determination to achieve high QC, and quite possibly the economic incentive, a chess engine is neither of size nor complexity that is intractable to 100% no bug ideology, plus there is plenty of automated testing possible. PERFT for example should take care of all move dynamics, you can write your own stress tests and your own internal slow exhaustive validations, and so on and so on.
Hope you enjoyed the discussion. Have a nice day. Literal or metaphorical? Well, you decide.