They’re totally gonna get fucked by themselves .
The big telcos downstream to other companies that offer sim-only accounts (eg: i have a dodo acct, they resell optus). So they either kill the entire lucrative resell part of the business, or inevitably face court because telling someone “oh this phone doesn’t work because you no buy from optus” when a slew of other people are literally using the same self-provided model on their network will be exposed as the massively artificial pile of shit that it is.