Episode numbers zero-padded to 2 digits
"The episode number prepended to <episode> is now zero-padded to 2 digits. This is reflected in the default output file name format."

Why? This is a massive PITA as existing downloads are re-downloaded when doing a --force.

Surely that is what --force is supposed to do?

From --longhelp:

--force     Ignore programme history

I suspect that you're always using --force, then relying on the fact that the download already exists in your output folder to prevent it from being downloaded again. Is that the case?
The BBC have often upgraded the modes and quality of their programmes and I may have downloaded at an inferior mode, so I have --force on to update them to the current preference. A good example is the 50 vs 25fps situation.

I normally move my downloaded programmes from the download directory after around a month to six weeks. However, in this case, I still had the programmes in my download directory which had been downloaded under the old rules (no zero-padding). Had those rules still applied under 3.18 then a re-download would have skipped a download. As it was, it downloaded the zero-padded programmes to sit alongside the existing non-zero padded with no benefit to the quality. Why change a default that's been around for yonks?