Televised addresses usually signify something important - not just an update on the booster programme?
Usually I would agree. However, I imagine Johnson and his spin team are trying to put as much media distance between him and the recent lockdown breach allegations.
If he does a conference with no questions he gets to have a "clean media appearance", which will mean the headlines tomorrow will be about this press conference and not his partying. He knows what he's doing. He's attempting to start the week with a clean slate.