There are two layers here. 1) You're absolutely right that the account ends up texting out a phishing link which any automated system would rightfully detect as phishing (regardless of whether the recipient has "consented" to receiving the message - it still contains a phishing link). But that's not the real issue, which is 2) Twilio's response to detecting the sending of a phishing link (possibly more than one) is to disable an entire account with no timely recourse from the affected account holder who may be running a legitimate business.
I don't think anyone is arguing that Twilio was wrong to detect the message as spam. It's more that an unexpected side-effect of the customer's current implementation had outsized consequences. Similar unexpected friction with Twilio's anti-spam mechanisms are likely to occur again and they will cause outsized damage to this legitimate business or others if Twilio doesn't change their strategy.
I'm the kind of person who would be mad at my choices in that case. If I failed to plan for that sort of thing it's on me. "What of someone sends abuse to my text message forwarder?" isn't all that out there of a question.
I should clarify that these messages are being relayed internally to me and like two other people. It would not be possible for someone to use out software to spam people. We are not a SAAS provider. We are a local service company.
I don't think anyone is arguing that Twilio was wrong to detect the message as spam. It's more that an unexpected side-effect of the customer's current implementation had outsized consequences. Similar unexpected friction with Twilio's anti-spam mechanisms are likely to occur again and they will cause outsized damage to this legitimate business or others if Twilio doesn't change their strategy.