I don’t think doing a refi or HELOC triggers a reappraisal – but completing permitted work can. And a lot of people do refi’s or HELOCs to buy themselves additions fancier kitchens.
We had a HELOC for part of our companion unit funding… it was paid off before we got occupancy. The HELOC never triggered a tax change. Getting occupancy definitely did. We’ve refi’d since then (no cash out, though.) and that didn’t trigger anything.
A friend had a similar situation – did an addition on their house – got hit with a tax bill once it passed final inspection.