Did you read the part where I quoted that SA is, in fact, official rulings now? It is new, so maybe you missed it. Here, I'll show you:
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Of course, as the bottom says and has been pointed out, a DM can always ignore them, just as a DM can choose to not use any rule or change them. Nothing new there.
Do you know what "official rulings" means? It means that whatever is in the Sage Advice Compendium supersedes any advice offered on Twitter. That's it. That's the only significance--the SAC should be taken as the definitive recommendation, as opposed to "public statements of the D&D team." It does NOT mean that the Sage Advice is elevated to the level of rules, or that Jeremy's suggested ruling applies to anyone's game. It is still nothing but a suggestion, and if you follow the Sage Advice in your game, it is YOUR ruling, because the only one who can make a ruling in your game is YOU (assuming you are the DM.) Jeremy cannot rule on your game, that's not how it works.
If a DM makes a different ruling on a published rule than what Jeremy suggests in his advice, that is not a house rule. A house rule only happens when a DM implements a new rule, or strikes a published rule from his game. As an example, the statement that "
if x, you can y does not impose a timing requirement and therefore the bonus action
y can be executed whenever the player chooses during his character's turn" is a ruling on applying the published rule. By contrast, the statement that "the Shield Master shove doesn't require the Attack action in my game" is a house rule, because it is changing the rules of the game, not interpreting them.
Here's an easy way to know which is which: if it is something that Jeremy can change his mind about, it is a ruling and not a rule. The only way to change the rule is with errata, that changes the actual words of the text and not just what you think those words mean.
Every single item in the Sage Advice Compendium refers to a rule that can be interpreted more than one way. That is why JEC has offered advice on that item--to tell people which of those possible interpretations he suggests adopting. If there is zero ambiguity in a rule, there is no need to offer advice on how to interpret it.
The "official rulings" designation serves only to try to address any possible confusion that might arise when a DM is looking for advice on how to rule on a situation and finds conflicting statements from Jeremy. Should I follow this tweet, or the the other tweet? Whatever is in the pdf is "officially" Jeremy's current recommendation for interpreting the rules in question.
Jeremy Crawford is not trying to make an "official ruling" for your game, that's your job. He can't do it! Every game and every group is different, and you'll note that Jeremy never says that everyone should follow his advice and implement his rulings. What he's trying to do with Sage Advice is to offer an internally consistent set of guidelines for people who need guidance. He can't tell you what's best for your game, he can only try to provide a generally applicable and consistent baseline. That's why, for example, even in the Adventurer's League, where the game is tightly constrained to the published rules and a DM's house rules are not permitted, the DM is expressly
not required to follow the rulings in Sage Advice.
The bottom of your clipping from the Sage Advice Compendium, by the way, does not say that "a DM can choose to not use any rule or change them." Obviously the DM does have that ability, but that's not what the Sage Advice Compendium says. It say the DM "determines whether to use an official ruling," not a rule. Rulings and rules are not the same. A ruling is an interpretation of a rule, not a change to the rule itself, and an interpretation of the published rule, regardless of whether Jeremy Crawford, you, Max, or Joe Pesci agree with it, is not a house rule.
