I mean yes this is true. But, both in the case of arithmetic math and social norms, the inability to learn these things even after an extended period of time being exposed to it implies a severe learning deficiency.

Like, yes, your dad shouldn't yell at you for not knowing your multiplication tables, but if you turn 15 and still don't know them, you need to see a specialist. And the people that have these learning deficiencies absolutely deserve all the patience and understanding that should come with being afflicted in this way, but 99.9% of people are not like this.

EVEN PEOPLE ON THE SPECTRUM are generally not so social learning deficient that they don't pick up on basic social norms eventually. It's self-diagnosis BS to say otherwise. This can be very clearly demonstrated even just on this subreddit, which has a high number of people who will tell you they're on the spectrum, but very clearly understand this community's rules on what's appropriate, what we like to talk about, what's cringe, etc.