That's not the case in my hybrid, the engine rev's when in Park. See John's post here that confirm the traction battery will be charged whilst doing this (albeit not by much)
During quarantine, Lexus recommendations are noted here; https://blog.lexus.co.uk/lexus-hybrid-parked/
I haven't seen much loss of charge to my hybrid battery since mid March, although it has had a good run to the shops occasionally. I don't tend to leave it sat for more than a couple of weeks max.
Provided you are keeping the 12v aux battery topped up, I wouldn't worry too much about yours being sat.