I have never participated in any kind of organized RPG play, so I genuinely do not know the answer to this question: What happens in an Adventurer's League game if the DM rules in a way that is contrary to the Crawford advisory opinion interpreting the rule in question? Does it matter if it is a Sage Advice pdf opinion vs. a Twitter thing?
I sometimes wish I had gotten into the Living Greyhawk thing, back in the day, but if there were rules gestapo yanking your credentials if you didn't strictly adhere to the infallible dogma issued ex cathedra, I'm probably better off having skipped it.
AL DMs can completely ignore Sage Advice if they wish.
From the DDAL FAQ
"As a D&D Adventurers League Dungeon Master, you are empowered to adjudicate the rules as presented by the official materials (PHB, DMG, MM, etc.). Run the game according to those rules, but you are the final arbiter of any ambiguities that might arise in doing so."
"Sage Advice (SA) is a great barometer for ‘rules-as-intended’, in any case. Whether or not your DM chooses to utilize SA for rules adjudication in is at their discretion; as always, the DM remains the final arbiter of rule disputes."
However, variant rules are generally not allowed: ALDMG: 'only the “Variant: Playing on a Grid” and “Variant: Skills with Different Abilities” variant rules are allowed for use.'
So an AL DM can't make up their own rules or include homebrew rules. An AL DM also can't use variant rules like flanking and other options from the DMG. However, in grey areas where there is room for interpretation they are not constrained to follow Sage Advice rulings or twitter ... they can go with whatever fits their current situation at the table best.
That is how it is supposed to work ... it doesn't always run that way so it is a good idea as a player to be relatively laid back about it.
Some examples:
-I know of an AL DM who liked to use critical miss rules and a few other things they just made up or pulled from variant rules but then used in AL games at a local store ... they didn't last long (a really good DM who made it fun for the players might be able to play this way as long as the players at the table were ok with it and it just increased the fun without affecting overall balance/objectives in the module)
- in a module I played in with a ranger/life cleric ... the DM refused to allow the life cleric healing bonus on a casting of healing spirit because they thought it was "broken". It didn't effectively matter in the circumstance in which it was used since healing spirit by itself was more than sufficient. However, there is no basis in the rules for the DM to make a judgement call due to being "OP" .. especially when the rules involved are quite explicit. 4 hit point goodberries can be another contentious issue even though they too are permitted by the rules. It is generally not worth arguing with a DM about this sort of issue but in theory an AL DM is supposed to go by what the rules say and not what they wish the rules would say.