Hello @RiannVS
From the link you have provided, it does state that they will only be disabling SMTP Auth for tenants where it is not used. This is further clarified in a tech community blog post from the exchange team here https://techcommunity.microsoft.com/t5/exchange-team-blog/basic-authentication-deprecation-in-exchange-online-september/ba-p/3609437 (This is linked in the page you referenced).
Starting October 1st, we will start to randomly select tenants and disable basic authentication access for MAPI, RPC, Offline Address Book (OAB), Exchange Web Services (EWS), POP, IMAP, Exchange ActiveSync (EAS), and Remote PowerShell. We will post a message to the Message Center 7 days prior, and we will post Service Health Dashboard notifications to each tenant on the day of the change.
We will not be disabling or changing any settings for SMTP AUTH.
Kind regards
Alistair