Why older capital ships would become treaty tonnage placeholders

What changes if the Royal Navy enters the Washington negotiations with more surviving battleships and battlecruisers?

Probably only a somewhat larger tonnage allowance; the old ships would mainly serve as placeholders until Britain could replace them with new construction.

More surviving capital ships would probably bring only a modest increase in Britain's permitted tonnage at the Washington negotiations. The Royal Navy could keep the older ships as placeholders until replacement tonnage became available, then exchange them for new construction. Their value in this counterfactual would include protecting future building rights.