It's not really a method to escape the law, or a technicality - it's that people other than Matrix.org are operating chat services, and the law applies to those people, but those people are not Matrix.org.

This won't save Matrix.org if legislators throw stupid at it, of course, but Matrix.org has the opportunity (though maybe not the resources) to engage with UK legislators to ensure they feel respected and that honest efforts are being made to comply.