Always thought discs were way too thin to be "straightened"?
Any warping of a disc will keep pushing your pads apart so your initial grab at the lever would feel unresponsive.
Other than that it can take a few goes at bleeding before getting them sharp.
Initially; I thought the discs were bent when i got the bike, turned out to be bent rotors, which i had straightened.
- Initially; I had the standard brake hoses, and the brakes were OK-ish.
- Then i got the hoses upgraded to braided and the brakes were crap.
- Investigation found the warped rotors, which were then fixed and the brakes were much better.
- Then i had a line leak on the left side so had to have the banjo replaced
- Now my brakes feel soft.
Likely as you suggest, and i suspect: They probably just need another bleed, though i don't expect to get them up to 100% without spending silly money on rotors, discs, callipers etc... but i'll never do that. Just not worth it considering the initial value and that it's a cat C, and the likely resale value -vs- investment.