Difference between DEM in XYZ and Tiff for same project

[flydrones]

Hello,

I did an export of my model (picture taken with a UAV of a terrain) and I did and export in TIff and XYZ. I left the max resolution (7.5cm), did not change anything.

I thought the XYZ would be points taken "on top of the DEM". But when I open both the TIFF anf the XYZ, I have some points that are 10cm above the DEM, and some that are exaclt at the same altitude.

Am I missing something? Isn't it just an export in different format of the same thing?

Thanks in advance,

Frank