Visited today on foot.
The signs are back! This time I went close to read them.
The chargers are open to the public. You pay for parking, and electricity is free. It says you can pay at the reception, or use PayByPhone app. All 4 parking have the same PayByPhone number and QR code. The QR code doesn't allow ad-hoc payment though, it just leads to their website that says to download the app.
It's 4CHF for the first hour and 3CHF each additional hour. That's not a bad deal, at 11kW it will be less than 30ct/kWh.
The sign also mentions it's included with the "E-Parkkarte" for guests.
There's a page on their website that I didn't see previously but it's not completely clearing things up https://www.villa.ch/de/facilities/ev-charging.html / https://www.villa.ch/en/facilities/ev-charging.html
The page still shows the older wallb-e charger that was installed before the easee stations. The ad-hoc price doesn't match, it says 4CHF first hour, but then 2CHF/h and max 14CHF, which is not what is written on the new signs.
It also says it's included in the parking fee for guests at 10CHF, but the reservation page says the parking fee is 5CHF with text below "E-Ladestation gegen Aufpreis" / "Charging station for electric cars at extra cost". There's no mention of the "E-Parkkarte", but I guess that's the 5 extra CHF for night parking.