Yes you will need more endurance attribute to raise smiting to 275 and above. You will still gain full levelling exp and part unlocking points for smithing at zero skill growth though. So keep hamming and you'll hit 28 and get that attribute.
Keep in mind every level up of character level reduces all skill growth(all skills), so being that high of level with only smithing is kinda awkward and self sabotaging. I recommend only using companions as smiths, the parts are unlocked for your whole clan so they can all work together. But save char and family for more useful skills. You can make a family smith weapons to force a level up if needed though.
It's not fair, balanced, well thought out or anything but a **** up that you're so penalized for levelling up. It's not even conveyed by the game itse;f.