Again, EASA does not have a say in that. EASA does not make laws or international agreements, those are negotiated on commission level and decided by the European Parliament. And it would have required primary law to recognize licenses issued by a third country. It was offered to the UK of course, on a reciprocal non-time limited way, together with all other EU regulated professions. The UK declined. Same as with the other professions, the UK would have to make watertight assurances that it will be fully and dynamically aligned to EU regulations, following all judgements from the ECJ. Again, it was the UKs choice to decline reciprocal treatment, and the EU simply follows the letter of its agreements and laws, unlike the UK of course. It is basically the same case as with border controls. The EU had those running from day one, the UK is unable to do so and therefore does not fulfill the most basic WTO rule there is. Same for licenses, as it was unable to issue new CAA licenses in a timely manner it had to accept EASA licenses, not because it wanted to play nice, simply because it was unable to work properly.
Yes, those too slow to act fall through the cracks, that is always the case with a deadline. It has been nearly four months, by now one could have done a new initial EASA medical and the required ATO training and checks to get his EASA license, the 14 theoretical exams are apparently accepted in some EASA countries if written in that country, as are hours if properly documented.