A lawyer’s opinion is just that. It is not the law. There is a lot of dubious interpretation in this opinion, not least unsupported claims of what the law intended. The lawyer is clearly working for the pro-STHL group in your building which is another reason it should be taken with a pinch of salt.
The assertion that the law was only intended to refer to “normal” lets is an opinion. NCAT and an NCAT appeal tribunal might disagree. Otherwise it’s just lawyers saying what their paymasters want to be said. If lawyers only ever expressed the fundamentsls of laww there would be no need for courts.
Action at NCAT to compel the OC to issue breach notices for failure to identify tenants would go some way to clearing this up.