Chz
Stark Raving Sane
I think that's sort of been addressed elsewhere. The media suite is for official announcements of government policy. It's not suitable for party politics, which is what calling an early election is. Sunak can use the media suite when he's speaking as Prime Minister, but has to sit outside as the leader of the Conservative Party.
Johnson took it to court to get clarified.
Statements to the press by the PM should be factual.
Statements to the press by the Leader of the Conservative Party Rishi Sunak are not constrained by truth.
If it was just the factual - dissolution of Parliament is 30th May - it could have been indoors with the seal.