[czernobog]

This is interesting, usually it's the latter because the config is ran line by line

Also, if it's not too much trouble, would someone help me understand why such files are required to start with numbers? In this case it's 10-no-password.conf.

I have noticed similar structure for apt and many more packages

[glitchcrab]

A lot of software which reads drop-in files will load them in numerical (or indeed alphabetical) order. Obviously this is important if the order your config files are loaded in matters, but otherwise it's just become a convention so people do it even if the load order doesn't actually matter.

[47282847]

Typically, config files are merged into one by loading them like ./conf.d/*, the order being determined alphabetically from their file names. You do not need to use numbers but they help to see that order.