How an H3a battlecruiser could raise treaty limits

What would H3a battlecruisers mean for the Royal Navy and naval treaties?

Their existence could push the negotiated limits toward 18-inch guns and roughly 40,000 tons.

If the Royal Navy entered negotiations with such ships, other powers could not easily ignore their calibre and displacement. An 18-inch gun ceiling and standard displacement around 40,000 tons become plausible consequences.