Storing bare minimum data in MongoDB

In a collection, there is a boolean field. For this field, I want to store the bare minimum data. For example, I only plan to store the value true. For documents where this field has the value of false, it is simply not stored at all. This scheme contains just enough information to make the distinction. If, in addition, I also store the value of false, it would be superfluous data.

What are the pros and cons of this minimalist strategy?
In what scenarios is it used?

I am a big fan of only storing true values for Boolean fields. This, with partial index seems to be a good way to reduce the amount of data stored while making some queries (the one including field:true) in their conditions more efficient.

I often go further and rather than using field:true, I use a timestamp that indicates when the field became true.

Rather than

is_active : true

I have

activation_date : 2022-12-05

This way I have more information in a single field. The existence of the field activation_date indicates that the document is_active and when it became active. Two birds with one stone.