Was the tiling done poorly here?

When tiling inside corners, one tile edge must overlap the other.

The finished tiled inside corner does not exist with you yet and would be the edge in the 2nd picture.
There, a tile covers the edge and thus there is an overlap.

One has to see how it looks finished. Only completing all work steps makes a job ready for acceptance. The silicone joint actually does the trick.
But it can indeed be that the professional does not see a few millimeters, while the client meticulously measures every millimeter.
In the end, the tolerance dimension counts.

The finished tiled inner edge is not yet present at your place and would be the edge in the 2nd picture. There a tile will cover the edge and thus there will be an overlap. You have to see how it looks finished. Only when all the work steps are done is a job ready for acceptance. The silicone joint actually does the trick. But it can indeed be that the professional does not even notice a few mm, while the client meticulously measures every mm. In the end, the tolerance dimension counts.

...I had indicated mm instead of cm in the original text (sorry). Therefore, the gap between the tiles in the corners is 8 mm! sealing that with silicone is quite challenging, isn’t it?

...I had originally indicated mm instead of cm (sorry). Therefore, the gap between the tiles in the corners is 8 mm! sealing with silicone is quite challenging there, isn't it?

Wait and see. Or what does "challenging" mean? I think it is wrong to point out defects now when there are none yet. This work is not finished yet.

Wait and see. Or what does "sportlich" mean? I think it is wrong to point out defects now when there are none yet. This work is not finished yet.

But you can already clearly see that the tiler should have become a baker instead. But silicone and makeup can, as always, hide a lot..