This is due to the UX desires to have the calendar list form fit with no scroll bar if they can all fit on a page, but then also have a min and max size boundaries (so it will scroll at some point if the max is hit).

I tried an alternate solution where the drawer and drawer container were 100% sized, to allow the .calendars list to set its size organically, but it hurts the animation that shows the drawer, since that animation is based on the size of the drawer element (which is 100% in that alternate attempt), but the content is normally closer to half that size.

By form-fitting the container to just the actual content, the animation then is over that visible content space, and has a better animation feel to it.

I put a comment in feedback-2 that hopefully explains that tradeoff, but also open to other thoughts.