Viewed a house today and noticed an uneven floor but the tile which was definitely old had no cracks whatsoever. No separation on any grout lines either. We would be replacing these floors if we moved forward but does anyone have any idea what it could be from? The walls, ceilings, exterior visible foundation do not have anything that appears too concerning just looking at with an untrained eye.

Also noticed this raised floor issue in the kitchen and laundry area. Both of these had a turtle shell appearance. Higher in the middle than the edges.

Red outline was a higher spot, blue was lower.

Can't tell how raised from the pictures but potentially just poor tile installation?

The highest spot is probably an inch high and probably an inch or so on the low spot. Both are about 3x3 tile areas.
The section in the kitchen ran in between the cabinets and was crowned like a road. Just seemed odd nothing was obviously cracked and showing separation.

Slab on grade foundation?

Yes, slab on grade foundation.

Location is on
Clay expansive soils that can lift 6-8" w/2-tons/sf force when wet?

Originally a Spec.house? (Search Property Tax History)

Neighbors exhibit the same?

The absence of exterior cracks & at fenetration corners stiff-arms SOP foundation suspects at first, ergo a mystery with facts presented thus far.

Don't think it would be clay soil. Maybe black ground or mixed ground.

Yes it was probably a spec home. I was hoping someone would be able to give a good guess of what it could be but understand that's difficult without looking at personally. First time home buyer so was curious more than anything

Edit - neighbors foundation and bricks didn't have anything noticeable on the sides/fronts from a distance.

If you don't invest in a Structural Engineer site inspection, then I would advise family to PASS on this one.
Without evidence in hand, I have run across spec.houses with poor foundations and sub-surface water leaks that exhibit other traits similar but not exact to this. The tell-tale cracks in exterior masonry and gyp.bd cracks over fenestrations got a pro to cover up but these are temporary to make the sale. Look for fiberglass tape/float paint in gyp.bd. Patching mortar is easier to spot.

The other suspect is a rare poor conc.crew finishing the wet concrete that can't float or
something sub-surface heaved before the concrete could cure, which raises questions about reif.steel conformance with Codes equal/better.

Would love to learn the real deal if ever discovered and different from above.

Thanks for all the info, this is the kind of stuff I was wanting. The house hadn't been on market for 5 days and my realtor talked to listing agent after I viewed and she said two offers were coming in that evening. This being my first buy I was wondering if the people offering knew something by the looks of the situation I didn't.