Certificate Transparency makes public all issued certificates in the form of a distributed ledger, giving website owners and auditors the ability to detect and expose inappropriately issued certificates.

https://en.wikipedia.org/wiki/Certificate_Transparency

No, it is not "insecure." It aligns with OWASP guidance: https://cheatsheetseries.owasp.org/cheatsheets/Forgot_Password_Cheat_Sheet.html

When would it be problematic? It would be problematic if they sent your actual password in cleartext as part of the "reset." This would show that they can access your password in plain text within their database, which is the worst way of storing passwords on servers. (Dedicated password hashing algorithms exist to securely store passwords.) What they provided you is a one-time password.