What makes you think it was not applied properly?

Which direction is north?

I don't have any photos, but I remember the tilers I have used had a notched trowel that had smaller "teeth" and more coverage.

Google "proper trowel pattern for laying tiles" and you will see photos that show what i am describing.

As a homeowner who has had thousands of sq.ft of tile installed, I would say, from what I have observed, that your tiler is not following best practices.

• Anvil 1/4 in. x 3/8 in. x 1/4 in. SQ Notched Trowel - For applying thinset while installing 8 in. x 8 in. to 16 in. x 16 in. tile
• Custom Building Products SimpleSet 3 1/2 Gal. White Premixed Thinset Mortar

"Application of SimpleSet Product

"Use a properly-sized notch trowel to ensure proper coverage under tiles. Using flat side of trowel, apply skim coat of SimpleSet with appropriate size trowel. Apply additional SimpleSet with notch side of trowel held at a 45° angle to the surface, combing in one direction."

There are some interesting YouTube videos on why that swirl pattern in the thinset does not actually hold it in place correctly. Some of the ones I have watched are by tile coach. And some are just super fascinating where they’ve tiled with thinset using plexiglass, so you can see what goes on with the adherence.

I appreciate everyones comments. Another question Does old thinset need to be removed completely?

The thinset was not applied correctly. I'm assuming from the pictures there was a cement board or other underlayment over the OSB? Those were large tiles to be laid over just one layer of OSB.

When properly installed, you're not getting any tile/thinset up larger than a penny. Looks like yours just popped right off.

I shoveled up a kitchen and bath floor a decade ago which came up easily except for one tile that had been properly repaired. It took as long to get that one up as it did to remove the rest of the floors. Excruciating.