The distinction surely isn’t re. “SP style” restaurants. Classical fine dining is just as likely to take 3 hours and be the only possible event of the evening?
But I don't think that's right. When I go to a L'Ambroisie, yes, I order half portions, and a long menu, and it takes three hours. That was the case with some other patrons when I went there, but not the case with others (a similar example at L'Arpege is seeing a couple order a lobster and bottle of wine each, that's it). Contrast with Willows Inn - where everyone is seated at the same time (or a slight stagger), and dishes are precisely timed with all deviations being pre-planned. It's a wonderful meal, but one that has as singular primary purposes. It's not a great place for a business meeting, or a date, or a good place to tuck into a single plate of something both immaculate and comforting (unless you want a half portion, in which case they can do that). Or, if someone told you that you could only eat at L'Ambroisie or Brooklyn Fare, I think you'd probably choose Brooklyn Fare. Now, if someone said that you had to choose one or the other for three consecutive meals, I think that the choice may be different. I don't mean that as an implicit critique of the Brooklyn Fares, it's more that an SP style restaurant is built for a different purpose.