KNX/EiB: Bus vs Powerline in a motel - arguments for bus

I came across a project for a small (~700m2) motel, where the Investor requested KNX based on 230V communication and not on green cable. It seems to me that due to the possibility of interference, powerline is only used in existing buildings where running an additional cable requires forging.
Am I wrong? If not, what arguments should I use to knock this idea out of my head. The price argument is not working. I'm afraid I'll be called out every few days for faults caused by "interference from the air conditioning" rather than faulty KNX workmanship.
Or maybe one of you knows of a large facility based on e.g. Powernet and can confirm that there are no problems.

Small assortment on the market, rarely used (customer doomed to experiment on his own body), heard that there are problems in powerline

Thx:)
And do you have any leads on any studies showing problems with powerline? Technical article, manufacturer information, forum thread.

Wg you will not find such material. Heard means more or less a conversation over a beer with someone who told about someone who was running and had big problems with it. The truth is that such solutions are hardly ever used. Very low transmission (1200 vs 9600), you have to be careful with protections (I guess those with low denominations can suppress transmission - also heard), I guess only ABB produces KNX.PLC. Poor power quality, unstable voltages etc are a problem. So if someone plugs something into the grid in a year's time, there's a good chance you'll have to account for the poor performance of your automation installation.
PS. I don't often sit on the electrode, email if you need anything.