Not that unusual. You really need to be careful getting the gunck well coating all the way around to be totally airtight. Maybe not the case with a specific tubeless tire.
My normal procedure is to check the pressure before going out.
I don't do my own maintenance (except for the very basic stuff). The bike shop did the tubeless conversion for me. Hopefully they did a good job for the 50 quid I paid them. I think the tyres (and wheels) are designed to be tubeless.
The tyre is holding it's pressure so far.