I agree, but I think that discussion of balance not needing to be as tight as a lot of DMs worry it does would have been far more valuable than the straight answer.
I disagree. He won't convince DMs in general that they could allow one player to play a gestalt fighter|wizard, another to use feats and MC, while another just plays a simple single classed character, and the game won't break. It's true, but you can't convince people of it who are convinced already that tight balance is required.
What you can do, is ease someone's worry on a particular issue, by pointing out that the thing they're worried about is actually working precisely as intended.
Some middle schoolers can grok GURPS and Rolemaster while some adults with master's degrees bounce off those systems hard. What's your point?
The rules cannot reasonably be called difficult to understand if people of all ages are able to easily understand them.
Sure. And it would be even more easily resolved if the designers would have written the game in clear and precise language.
Probably not, since most of them are cases of people just failing to actually read the rules. The same thing happened in 4e, where the rules where
very clear and precise, even in cases where there was no rational room for secondary interpretation, because people see what they want to see.
The constant rules questions and the ever-present ambiguity in the rules suggests otherwise.
Not really. Primarily, because I think you'd have to back up the idea that these questions are at all "constant" or that ambiguity is "ever-present".
Secondarily, I don't think that the questions and occasional ambiguity do suggest against the claim that 5e succeeds in being clear enough to sit down and play while leaving room for interpretation. Most people aren't on twitter asking Crawford questions.
I don't have the tools to confirm or falsify this, but if I did, I would be willing to bet significant money that the amount of online traffic about dnd that is rules questions is enormously outwieghed by the traffic that is just people talking about their last session, their homebrew and houserules, their OCs, their favorite actual play, making jokes about class stereotypes, and other non-rules-questions related content.
Most groups find something that could go either way, someone notes what seems obvious to them as the best way to run it, and that becomes how that group runs it. Hell, that happens with rules that don't really have multiple ways they could go, because people don't most people don't care about RAW they just want to have fun.
And because the rules don't get nitty gritty with every last thing, and aren't written in legalese, people feel much more empowered to just play the game how they want.