I've got no idea where you're going with this. Of course moving around between countries during a pandemic is risky, no one's saying anything different, but that's handled by the countries involved. If the UK allows residents to go abroad and the countries they're going to accept them, it's got nothing to do with the EU whether they're working or on holiday, it's up to the UK and the other country to sort it out safely. Can you imagine the furore if the EU had stopped UK holidaymakers going to Spain?
The link you posted is about Guinean workers in Spain, so it has even less relevance to Romanian workers coming to the UK. Just to point out though, post-Brexit, we'll be getting seasonal migrant workers from even poorer countries than Romania or Poland and those workers won't have the current protections and rights the EU offers so they'll be even more prone to exploitation.