Yes, but if the restaurant pools tips, then that's how they do business, and it has nothing to do with how you pay the tip, unless (again) you want to help someone defy their employer.

I have nothing against cash tipping at all; I do it all the time. But the only "benefit" it seems to have over card tips is that it makes it easier for the waitstaff to (if they want to) cheat either their employer or the IRS.