I had a long discussion with my DPE about this topic on my CFI ride, and he had an interesting interpretation of the regs.
He was of the opinion that when you endorse a student pilot to solo, the endorsement includes listing a *specific make and model*, and if that make and model happens to be tailwheel, that you *don't* need to give the student a tailwheel endorsement in addition. The logic is: the specification of the "make and model" kind of "implies" tailwheel inherently, and the separate tailwheel endorsement is redundant. (The same would be true for complex, high-performance, etc.)
I had never thought of it this way before, or heard it thought of this way before... But my DPE pointed out that a *solo* endorsement only lasts 90 days, whereas the tailwheel endorsement lasts *forever*. So you can do it this way to effectively issue a tailwheel endorsement with an expiration date on it. A CFI *might* want to use a strategy like this with a student pilot, because what if they solo in a tailwheel, but then switch to some other kind of plane for the rest of their certificate...? You might not want to have your signature on something that carries such permanence.
It still seems a little weird to me. But I heard this from a DPE on a CFI checkride! So there's some food for thought...