Obviously visibly works. I think arrangement is important:

-vf "tblend, framerate=60.000"

Can't confirm by eyes, even by frame-by-frame:

-vf "tblend" -r 60.000

Of course the source video must have less frames (eg. 30 fps) than the desired one (eg. 60 fps).

Then, it's quite wiser to use up to 3 decimal points (eg. 60.000), since sometimes the result ends up like 60.001 fps, so concatenate would not work.

The -r option is also too dominant even if both -r and -vf framerate= are used.