Yes, correct but that is not your situation.
You own one property and are renting out the entire property. It is not your sole or main residence. You live in a separate property that is adjoining but it is distinctly not part of the same property. Both properties have separate titles/deeds so you cannot describe as a self-contained unit just because it was once part of the same building and continues to share a party wall.
It's very clear to me that you are incorrectly claiming this relief and that you have made incorrect assumptions about the self declaration. As
@NoRegretsCoyote has pointed out, the burden is on you to accurately declare information that you submit.
The simplest way to distinguish it is whether they can be sold separately, which in your case they can because they are two independent properties. The "attached but separate" that the rent-a-room refers to is access to the property. You and your tenants can have separate entrances and not share any common space but ultimately it is still a single property that could only be sold as one property
It looks like you need a new accountant as well as new FA...