That's such a ridiculously nitpicky thing. Nobody cares if the Tonight Show airs before midnight, nobody cares if the show they watch at 11:35 is called the Tonight Show or the Tomorrow Show or the Jay Leno Show or whatever.2. Bumping the Tonight Show back an hour no longer makes it the Tonight Show, but the Tomorrow Show or the Really Early Today Show, which trumps 50 years of tradition and format (imagine if the 35 yr old SNL was taped on a Tuesday, shown on a Wednesday).
And to use your example, Saturday Night Live has been airing special Thursday episodes for the past couple of seasons and doing pretty well in that timeslot. Nobody cares that a show called Saturday Night Live is airing on a Thursday, they just care if it's funny or not.
Sure, they could have renamed the Tonight Show when Jay took it back, but what would be the point? NBC wanted everything back the way it was. I'm assuming the mantra now at NBC is that if it's not broke, don't fix it.