The only thing you would really stand to lose from selling then buying from within the TFSA vs. transferring directly (in-kind) is the difference between price when that happens and transactions fees that you pay for each. (If you pay $0 in fees then it’s not that big of a difference). And you would need to have or move in the right amount of cash first, if your broker gives you back your funds back slowly.
The advantages with having stock in TFSA is you pay no tax if it grows, but you get no tax break if it shrinks.