Oh yeah, agreed. Time stuff I can sometimes imagine the author sitting across from me, staring me in the eyes with a stern expression saying "And. It. All. Worked. Out." before I can even start my time travel question.

Which is reasonable, tbh.

I usually think of hard scifi as being internally consistent, or consistent with the real world, with rules and implications of that considered and explained (or at least obeyed). I think it's just a genre specifier, although most geeks I know enjoy reading hard scifi over more hand-wavy stuff.