It's a matter of risk . . . .
At TC+3, there's an increased chance of pulling a 10 to match your 11. But if the dealer pulls an ace you're doubled bet is toast. If you pull anything other than a ten, the dealer is favoured to win - so again the odds are your doubled bet will go south. You could help the call by keeping a separate ace side count so you know how many aces are left in the shoe - although most contributors here agree that for a six deck shoe using hi-lo the advantage of doing so just isn't worth the bother.
I personally wouldn't double 11v10 as, despite the mathematical advantage, as the risk is too high. Same reason I don't double against a dealer 2,3,4 when at TC+3 or higher when I've a "big" bet out. The chances of the dealer pulling a 9,8,7 followed by a 10 are always there and losing a 16 unit bet when I only start a session with 40 or 50 is significant.
To put this in perspective,I play a 1-8 betting ramp and my sums show that when playing all the long term advantage is just a little over 1/3%. But then I don't do it with any expectation of getting anything other than some free adult entertainment.
Does this help? Are you in the UK?