Why is solar grant work carried out on basement flats if not included in helping EPC’s grading?

Hello, I own a block of 6 flats and have managed to get solar to 3 flats under a grant scheme due to the tenants being in receipt of PIP.

I had an EPC on my own property due to trying to sell, and talking to the gentleman carrying out the survey, we got around to the 6 flats, explaining that 3 of them had solar installed, I asked the question. I have had solar installed in 3 flats, one being a basement flat, surely this helps on the EPC? The reply was a surprise, two of the flats yes, the basement flat no, as it had no roof space

There is a section where the calculation for solar has to include the flat roof space, not the property’s roof space.

I suppose the question is, why is solar grant work carried out on basement flats if not included in helping EPC’s grading?

Thanks,

Matthew