If the lender is a non-ADI (so the typical 2nd tier lenders like Liberty, La Trobe, Better Mortgage Management, FirstMac and the like), then the offset account isn’t a bank account, because those lenders are not banks that have the $250k ADI Government safety net.
Legacy LRBAs from banks like St George/Westpac/Bank of Melbourne, CBA and the like with an offset are all good (though off memory, I don’t remember CBA offering this).
That being the case, the offset account is the same as the loan (quarantined on paper, but not in reality, because they aren’t actually a bank who can take deposits), and so redrawing for any reason not allowed under s67/67A is considered a new loan. Repairs and Maintenance and certain exemptions apply, but say for arguments’ sake the rates were paid, this is a borrowing not to acquire and a breach of s67.
Rent going in is fine.
Having said that, it is generally not a big enough breach to be material enough to qualify, but it is a management letter point with a need to fix in future, as trustee behaviour test may apply for later years.
Best practice is for the SMSF to have a bank account with a bank, contributions in to that account pay the expenses from the same account. Rent can go into the offset.
Disclaimer: general advice and my frank opinion that the ATO are splitting hairs with this and would be better placed using their resources somewhere else.