Whilst that old saying likely won’t be going anywhere, I think the idea of a prop not hitting their straps until later in their career is becoming slightly outdated.
It came from the notion that a good prop would ply their trade at club level, going up against the old heads and learning more over the years. That simply doesn’t happen anymore.
For better or worse, with development pathways in place and talent identification, even props are brought into the system early on. From recent memory the only ‘project’ prop in the current setup would be Pone.
If we look at some of Australia’s more recent props such as Slipper, AAA and Sio, their scrummaging has been consistent since they first came onto the scene. I’d argue they’ve actually been able to have more consistent careers over a longer period, instead of suddenly becoming more adept at the back end.
Bell’s scrumming isn’t bad by any means and if he’s able to maintain that consistency over another 10 years, he will have a great career in gold.