If I was analysing TB's of data via SQL, yeah i'd probably agree its better not incur the transfer overhead to perform this check - if it was small org, id say its not great.

Also once you start saying "i want secondly/minutely breakdowns", the dimension (neat term) gets pretty...large (probably less than the TB of data though)

It can. A function that generates date objects between two date objects is also pretty performant for specific uses.

Joining against a generated series is also trivial.