In short why we like to have join in UPDATE or DELETE

Select * from Bills
inner join Accounts on BillAccount = AccountID

is faster than

Select * from Bills
where BillAccount in (select AccountID from Accounts where BillAccount
= AccountID)

so we expect that

update Bills set
BillValue = 100
inner join Accounts on BillAccount = AccountID

is faster than

Select * from Bills
where BillAccount in (select AccountID from Accounts where BillAccount
= AccountID)

and join with UPDATE more easy to filter when use WHERE

update Bills set
BillValue = 100
inner join Accounts on BillAccount = AccountID
where AccountKind = 1


But update 2 table or more in one shot, i think is not logically for me.