Erm but you can add a specific custom clause yourself. It’s totally straightforward.
I happen to agree that specifying when initial payment to be made more exactly would be good for both LL and tenant to avoid any confusion. The OR draft equally says little on ventilation and nothing on what happens if a tenant leaves possessions behind after tenancy. But OR won’t change their new APT template 2 months after use unless lots of LLs complain..
We all have different things we’d like to have in the standard OR template - there is a lot more detail in other APTs. For example the original gov AST allowed you to not only specify a date but also whether payment would be cash, cheque, standing order. (Source: GOV.UKNo longer available - GOV.UK )
Some tenancies have gardens or pets where extra clauses warranted etc etc