Just for clarification: does aburi refer to the act of searing only
or does it include searing, pre-marination, and/or toppings (e.g.
minced gari, negi, garlic, ponzu sauce etc)?

I just noticed that the best kaiten sushi place in my area (the only
one that is run by Japanese!) offers a aburi maguro zuke. The cut is a
bit above regular maguro, but not quite chu-toro.

Certain sushi items certainly benefit from the searing/aburi and/or
pre-marinated/zuke treatment. The guy who I think benefited from my
idea of maguro tattaki in Osaka, who "invented" otoro-tattaki started
serving something quite interesting 2 years ago. Basically Japanese
hamachi sushi; the fish is quickly seared/heated on the grill, and
served with a dash of a Japanese spice on top (a dab) that has flavors
of lemon (yuzu?) and pepper on it. Quite a unique combination and
taste...is this popular in Japan?
Same guy also serves Japanese snow crab nigiri with dabs of kani miso
on top (only upon request!)