Pressed post too soon!
Yes, I realise that you are talking about later in the year but it is very much not the case at the moment that drivers are just swanning around mainland Europe with nobody asking them for any documentation.
Several areas in the north have just been put back into lockdown for 4 weeks. The whole of France has a curfew - which changed yesterday from 6pm to 7pm - you need appropriate authorisation to be outside of your home after curfew. Only very limited reasons are acceptable.
No restaurants, cafes or bars have been open since October. Takeaways are permitted (but not after 7pm - see curfew above).
New cases in the last three consecutive days have been 29975, 38501 and 34998.
I would absolutely love to think that by June we can just go where we like and cross the borders (just like in the old days!) but many people are assuming that the lifting of restrictions in the UK will apply everywhere on mainland Europe - that is very much not the case at the moment and it will take some sort of miracle for that to occur.
I don't want to be all doom and gloom, there is nothing I would like more than to be able to travel to see family (with a valid vaccine passport) but it is very simplistic to think that you can just get to Fraance and then go anywhere without having to comply with assorted local regulations.
I think a lot of posters on here who have had to commute across land borders during this pandemic will be a little puzzled by your assertion that these borders don't actually exist.