Firstly DV takes approx 12 months to complete, if they find a huge red flag they say no a little quicker. PM won’t have been appointed and had vetting done the next day.
people can still do the job they are appointed to in some areas , but won’t have full access - so completely possible to be allowed to start a job subject to obtaining vetting later.
secondly the entire process , what’s involved and who is aware of the result is completely classified and only those who hold vetting themselves should be aware. The rules are very strict on this and discussion of someone’s clearance level is not allowed!
i would imagine the officials who work in this adhered to those rules - they are strict and sharing a status is a serious breach.