That's crazy. Perhaps a good comparison is the channel tunnel, e.g. going from London to Paris you go through security similar (a bit less onerous) to that at an airport before boarding.

That was the case even with the UK in the EU (maybe it's not any less onerous than an airport now actually, idk) but otherwise intra-EU over land is not an issue, almost necessarily. (But then, you might think that about Canada/US.)