It's the opposite: if they say they'll string fiber in 2 years, they get drowned by anrgy requests for status updates if they slip. It's lose-lose for them: commiting to a delivery date gets people angry at them if they slip does to regulatory/admin delays, not commiting to a date gets people fed up and impatient.
I'm not saying that they should specify how soon fiber is coming. Yes, then they'd have a support issue as you describe.
I'm saying that they should admit it when they know that fiber definitely isn't going to come any time soon at all, so that people can make an informed decision not to waste their time waiting for it to come.
I can't speack for Sonic but I feel like they might not know if something is impossible to deliver in the short term, and the amount of work to give you an accurate timeframe is non-trivial, so they don't do it. To them, there's probably no difference between the "we want to do it but we don't know by when" and "we want to do it but we don't know what's stopping us", since I guess all their delays are unknown unknowns.
Sounds like you'll be waiting for microtrenching anyway, good luck