It’s not so much about passengers as staff (although social distancing is very difficult in a Mk5 lounge car unless you keep the passengers so far apart that the capacity is minute and the lounge car simply isn’t worth running*)- the staff also need to distance from each other physically, and now that the new stock is without attendants’ ‘pantries’, the only place in which the staff can have a socially distanced rest area is in the lounge car seating (and possibly the seated coach). There is no way that staff and passengers could share this area in the current situation. Another issue is that physical distancing is required in kitchens too, rendering it very hard for the catering service to be provided effectively (as the current lounge cars are generally designed for two persons to run them).
I‘m sure someone who works for CS will confirm this, and probably other reasons why the lounge car cannot operate at this time. I am very sure that there are very good reasons why it can’t operate. After all, it’s marketed as a significant attraction of the service- so if there was any way in which it could have been operated in a Covid-safe way for the tourists in late summer, I’m sure CS would have opened it.
*Remember that under normal circumstances, it is generally expected that solo travellers/couples will share those booth tables with strangers. That, of course, is impossible in Covid times, so the capacity is significantly reduced. Then, when entire bays of seats have to be marked ‘out of use’ (or screens installed) to comply with the two-metre rule, it becomes more trouble than it is worth to operate. Also, who really wants to go to the lounge car to sit away from everyone else behind a screen? That really isn’t what the lounge car is about, and definitely not the experience that CS want people to have.