lololol You can't be serious. Haven't you played there? I'll be DK and cargo throw you into the giant worm thing.
I can't say I've ever seen anyone die to the Bulborb.
Anyway, though, why would it be a bad thing if DK could do that during a small window of time on one stage when IC's can infinitely chaingrab anyone on any flat stage? If he manages to get a grab off close enough to the Bulborb during that short amount of time it's possible and while the opponent is aware of the danger, then he deserves the KO.
Even so, I went and tested it. I had a big long wall of text written about it, but that's silly, so I'll just sum it up:
-DK has to go low enough to hit the tongue with the throw that he will probably SD
-It takes long enough to get that low that the opponent should be able to escape
-Try the same movement on Corneria and you'll just throw them right off the edge. It's actually easier on Corneria, plus you can do a horizontal hop instead and actually survive while still throwing them off since the boundary is so short. Also, they have less room to escape your grab while in that tail area.
-Hold them for that amount of time off the edge of a normal stage and it will usually kill them anyway because a fair amount of characters can't recover that far, so it's sort of insignificant
So, basically, if you let yourself get hit into the Bulborb's mouth and don't manage to escape either, you probably would have died anyway. The same pretty much applies to anything else that could hit you in there, which isn't much.
Another thing, if you stand on the Bulborb's back and jump up and down, it will never eat you. It doesn't randomly eat people on its back like I had thought a while ago, it's just based on how long you're standing there. Tested for quite a while and no random bites.