It's complicated.
tldr, Sammy's a guy I'd share a bottle with, but not someone I'd go into business with.
Alex and Ted disagree on this. Ted thinks that Sammy ultimately broke up Van Halen; Ted thinks he could've gotten the band back together if Sammy hadn't gotten involved. Alex instead thinks the breakup was a long time in coming, something that had built up over years. Ted and Noel blame Dave for going off and doing his own things; Alex actually blames Ed for doing "Thriller" before that.
It's really complicated.
But yeah, by simply never mentioning Sammy or the Sammy years, I think Alex says more than if he'd written chapters on the topic.
Mike and Sammy remain friends, and Mike more or less got screwed by the brothers, so I see why Mike has more or less taken Sammy's side on things. But pretty much everyone else, oddly enough INCLUDING Sammy, says that it was Dave that more or less made that band successful. Ed would otherwise likely have been this guy that guitar guys knew about, like Yngwie or Vai, and not the massive household name they became.
In general, Sammy says things that are often easily disproved, and that casts doubt on the rest of what he says, especially when literally everyone else is saying other things.
It's a mess.