I do not use electricians, all my meter installs, load centers, and dedicated circuits I installed to NEC code myself. Although I have been involved with other people in my area that used electricians and they have just been more curious then anything. The miners never really concerned them under any circumstance. Only thing I can think of is your electrician maybe worried about the load you will put on your 30A circuit he would installed, so he wants to replace the cheaper Square D load center with something of higher quality GE, Siemens, etc.
Do you know if your Square D is using an AL bus?
I don't know for sure. The ones he was going to replace were 110's 10 and 15 amps so really not needed. It's worked great for a few years. He also called it a Main when I called him. Somehow he thought it was a Main not a subpanal. So sounds like there was further mixups. I'm not sure if he was trying to cheat me. Or with the amount of times he said I should get a 2nd quote if he just did not want the job. Which is weird since he did a free quote, and the company does a great job on cooling/ac's. But this was first time to try their electrical side of business.
Only reason I can think of to replace the panel if you have room for the breakers is cause it has an AL bus and he thinks you will do a continuous load more then 80% which AL can handle just a little safer to do with CU buses. I am not a electrician but if it was me I would not replace it for a 30A circuit, a 60A+ yes but not a 30.
BTW: 2 Pole 30A Breaker, 10 ft of 10/2 Romex, and the outlet box and cover plate is like $75 of parts.