My husband is a plumber and would strongly advise against it. There are important reasons why manufacturers advise larger cabinets (at least 3") for sinks.

If you figure it out please post a follow-up! Because I have been wondering the same for sinks for my 30" base -- some seem like they could just squeeze in but how do I know? Putting only a 25" (21" interior) in a 30" base is such a waste of space!

I guess the only way will be to order the sink and try it, send the sink back if it doesn't fit.
My cab will be frameless too, so not sure scooping is even a option there.

Someone else asked about using an undermount as a drop in, as well. I would like to do that, I like the look of a narrow rim but wonder if it is not enough to support the sink.

I assumed that the extra inches were suggested for the mounting hardware, but the sink itself would basically be sitting on the sides of the cabinet and sandwiched by the counter. Then a couple wood supports under the sink for extra security.

raee-I know most undermount sinks don't have a finished rim, so placing as a drop in would leave a potentially sharp or ugly edge. I think I will order the sink and just see what happens. Worst case scenario, I have to send it back. Best case, I get the biggest sink I can possibly get. Do they make 27 or 28" sinks to better fit the 30" base?

No, that is the puzzling and frustrating thing! I am finding 25", then they jump to 33" -- but just as with your sink, some of those 33" sinks seem to be only 28.5 or so of sink itself, and angled slightly in like your Blanco, so maybe could fit? I have to remember that the 30" will be the exterior measure, not the interior space, that I guess would be about 29" -- same for your cabinet?

raee- I saw a few 28" stainless while browsing yesterday. Franke and Blanco both make stainless undermount that fit in a 30" cabinet. Not sure what you are looking for though.