Is non-resident tax is the same as income tax?

I think the "imputed tax" as part of your non-residence fees to cover possible rentals is a bit of a myth. It is described on Spanish government websites that you obtain a benefit by having use of a holiday home in Spain and you are taxed on this benefit. I supposed they get you either way.
And having a holiday home in UK now means paying full council tax as they did away with the reduced rate. Buy one in Cornwall and you'll pay around £170 a month even if you only live there for a couple of weeks a year.
Our next door neighbour in UK had a holiday home in Florida and was paying nearly $6,000 a year in local taxes. This was on top of maintenance fees levied by the community. And spending more than 31 days there meant filling in a tax return.
Only two things certain in life............
Back to the OP. Yes, your solicitor was correct. Only the IBI (collected by SUMA) and the annual non-resident tax are payable. Of course, the bank will also charge you non-resident certificate fees and non-resident account fees but that's another story.