"floating" tile floors

I cannot help other than to say it's likely about $$$$

I’ve seen quite a few homes and apartments under construction here and have never seen that practice. Our floors have a concrete layer just under the tiles.

I've wondered about the rough surface but have never seen that process.I followed my sister-in-laws house construction & the rough floor was follower by a leveling layer of cement then tile, The same for my wifes daughters house and I'm assuming it'll be the same very shortly for my place. I'll let you you here if any different(or as you have witnessed)

Usually they put down a layer of whats called

thinset its similar to concrete but ver smooth

no sand or little pebbles in it and it’s applied  as they lay the tile …..what is being talked about above is whats called a dry pour usualy   reserved for pavers out in the yard ,  driveway, its mixed with very little water and put down about 2”  thick  on dirt and then they put the pavers on top and level w/a rubber mallet …..  i personally never saw it used inside ….maybe there wasn’t a cement floor and they put it down on a dirt floor and saved on the concrete pour when they built the house ???..  don’t   know for sure without seeing it…🤔

Thanks for the responses. So I just skipped through the older video of our house that a friend sent 2 months ago. He has the same type of house being build in the same block (it is a residencial) so I assume all these houses are build the same way. In the bathrooms it is most appearant because all the drainage tubes are layed out ON the concrete floor. Looking at the finished wall tiles they stop around 20cm above the concrete floor so thats the amount to fill up. All the other rooms were already filled level with sand/gravel.

So yes I think it is a cheap solution to cheap engineering!

Considering adding weight and volume and no extra strength this would not be my way of doing it.

In the latest video's the tile floors are all done and it sure looks good. I would not have known about this "solution" if the earlier inspection wasn't done.

I have never seen tile laid over gravel here.  Not once.  Only over a concrete slab many times.

I saw the same with the build of a new colmado, tiles cemented over a layer of gravel on a concrete slab, different contractor. Both in San Cristobal area, could this be regional practice?

It could be regional or just a way of cutting corners to save money.   It does not sound like a good practice, but perhaps an architect could respond.