Same with aerobatics on a A152 Aerobat. You can fly that Cessna as PPL, but to do aerobatics you have to have an endorsement (and the plane must be released to do aerobatics).
Can you provide a reference for this, and detail in which jurisdiction this applies?
As far as I know, in FAA- and JAA-land there is no legal requirement whatsoever to have aerobatics differences training. Sure, clubs and insurers may have their requirements (and rightfully so), but the lawmaker does not.
In contrast, a "conventional" (aka tailwheel) aircraft does require differences training by law.
But what in case you buy your own taildragger airplane within your PPL rating, and it's a single seater. So you cannot get an instructor with you. Or a rare airplane on which there are no instructors left- let's say you restored a Fieseler Storch. Does any taildragger training permit you to fly that Storch as PIC or is it type related?
As far as the law is concerned, once you have had your taildragger differences training signed off, you're good to go in any taildragger (that falls within your class rating privileges, eg. SEP).
But jumping into a challenging single seater might not be a good idea after just a few hours on an easy taildragger type. Most clubs/owners/owner associations will have some sort of example syllabus where you need to do a few hours on a type that closely matches the single-seater type, before they set you loose. And your first flight should be in very benign conditions, obviously, until you build some experience.