I think the DfE said work done so far. Apart from previously set coursework / NEAs where the planned deadline was already after 23 March, I would be surprised if this work being done online now is permissible as robust evidence.
Some schools have a full set of online resources and are still setting and marking work.
Other schools are setting no work at all and pupils have already been asked hand in their textbooks, so wouldn't have the necessary resources anyway.
Some pupils will have full access to the internet at home and will be encouraged (and possibly actively helped, especially at GCSE level) by parents who are able to support them.
Other pupils don't have access to a computer at home (or it is being used by a parent WFH) or may be caring for unwell relatives.
With learning at home, the playing field becomes more unequal and the conditions under which assessments are taken become less standardised.