last_updated_at updates automatically only for files in _pages directory

[Llannelongue]

Hi, if a .md file is directly under the _pages directory, then even without a last_updated_at parameter, it will display Updated: ... (date of last modification). This is very handy as it saves changing the dates manually.

However, for all the pages elsewhere (either in other directories or in subdirectories of _pages), this is not the case, and if the last_modified_at parameter is not used, then there will be no date displayed.

I haven't been able to track down where this difference comes from, any tips? (to be able to make all the pages behave the same way)

Thanks!