Short answer Ed is NO! There was no need. BUT, many of the old and tired No4T's passed(?) the 19T proof but were failed subsequently because the bolts were difficult to lift/open. This showed that while they 'passed' proof (?) the extra loading had proved too much for the sometimes marginal hardening of the locking surfaces.

I never quite fathomed out why the bolt would prove difficult to open in these such cases. Any ideas Ed?

Better just clarify that. Subsequently failed proof was as a result of the difficulty in raising the bolt lever immediately after proof and not subsequently, as in after years in service