Hmm, I certainly recognize what you're saying from D:OS2. I absolutely did not in any way attempt to "break" the game, but I found myself on numerous occasions confused as to why quests / quest givers were acting strange - and the most common examples in my case where finding objects / killing enemies that I had already encountered, or, doing the quest line unintentionally in the wrong order, or, quest givers acting strange when more than one number of criteria was met for conversations. Best example I can remember is that I couldn't at all do anything with the Demon Dude in the last act because something uniquely triggered his conversation once I got there, and after that he never even addressed as to why he had summoned me in the first place and refused to give me the allied-quest that he is supposed to offer...
I found that PoE dealt with this a lot better and not once during the entire game session did I feel like something wasn't working as intended, quest-wise. Despite me being *very* confused as how I would prioritize in the PoE2:D questline, so I did things in a... Rather random order. I played both PoE and PoE2:D for the last couple of weeks and not once did the quests in any way break unless you actually did something that was a legitimate criteria to breaking the quest (like killing the quest givers or important NPCs). A great example that comes to mind are bounties, I simply did all bounties unaware of their bounty state while exploring because I noticed that they had interesting loot - and much, much later I turned in *all* of the heads for full bounties. While this is hardly how the encounters were supposed to happen (and it is rather weird from a RP perspective that I went around carrying random heads), I was just happy that I did not miss out on rewards for a job that I had completed.
Not that this is quite the same as what you're saying, but it came to mind. If the NPCs (or guards, in certain other games) react to theft without witnessing it (*cough* has happened in D:OS2) and even as accurately as saying "YOU stole it", then I'd make a bug report. It feels like the NPCs, like you said, should react to the relic being gone - but they shouldn't be able to just without effort stare the PC down as the thief (unless they have a reputation for doing so? Not sure if BG3 have, or will have, a reputation system like PoE). I'd say, in this particular scenario, that them going rampage at the "outsiders" (read thieflings) would be a more logical reaction. Maybe the PC will see the druid guards yelling at random thieflings for stealing their artifact and maybe they'll stop you to search you where's you get some options in order to attempt... I don't know, maybe slight of hand skill-check to hide it, talk your way out of it, admit you took it or lie and say that you just found it (and later can specify whenever you want to frame someone or if you, less believable, just "found" it) and want to turn it in. If you even get some bonus "reputation" with the druids for "resolving" this (aka. lie), then it would play in the hands of evil-decisions-gives-profit-when-done-right.
... I mean, my proposal probably didn't make that much sense at all - but I just feel like it would at least be a more appropriate solution than the druids running at ya screaming "YOU TOOK IT!". However I do recognize the amount of work this would require.
... Lastly, you answer your question - I cannot remember BG3 at any point not tracking my actions properly... Yet, anyways. But I have really been making the most vanilla cookie-cutter decisions so far so that is hardly impressive. :')
