Actually a change was made a long time ago to default SMB Security off. It used to be that SMB Security off would be Public access, but because of security concerns, SMB Security defaults to off (disabled) and has to be set to the security level you want. Public is a security level, Off is disabled and not a security level.
Snippet of the Change Log:
2022.06.19
- Add: 'Public' setting to SMB Security settings to share devices public. The 'No' setting used to set 'Public' sharing.
Either you didn't notice till now, or you haven't updated for 7+ months.
No. Update often and read the Change Notes. Set the security level to the one you want, or off for disabled.