If you pay thousand of baht to an agent, yes, you wouldn't need to go in person. Just give them their passport and they'll do it. It's legal, but I don't see it worthy, tho.
I don't know you nor your details, neither you mentioned any. But, just thinking out loud, it might be they think you're not a real remote worker or they didn't trust your papers and gave this shorter visa as a trial test, after which you can get a regular DTV? It might also have something to do with you already having lived "too much time" before in Thailand with visas that weren't supposed to do that?