Depends on the modpack. For most modpacks, your answer is correct - Tinker's Construct tools are not enchantable in a vanilla enchantment table. However, I am currently playing Project Ozone 3 modpack, and (believe it or not), in that modpack, you can actually enchant Tinker's Construct tools. I have no idea how they did it, or what mod makes it happen. And I haven't used it at all myself, so I can't expand on it, but I mention it in case somebody wants to go have a look at the pack and see how they made it work.
P.S. They deleted my avatar image and my "join date" is from July 2019 (i've been posting here for at least 5 years if not far longer). Weird. (They show my first posting as Aug 27, 2013)