I want to communicate the implementation of this kind of bottom sheet to developers, specifically how it's a tall bottom sheet, but you can still see the background minimized underneath. What is this called?
Sheet, bottom sheet, bottom drawer, bottom modal sheet. Depending on who is more familiar with what system/nomenclature it may vary. I would recommend making very simple prototype that you can show off if you aim for a specific behaviour.
Personally, if the sheet is covering so much that you no longer can tell what is behind it then should be a full screen page. You can get over with a lot of content showing only part of it initially (if it makes sense for particular situation), and then allowing to expand the sheet to the full screen.
Here is an example from material design. https://material.io/components/sheets-bottom#behavior
This is according to iOS, a Sheet
A sheet helps people perform a distinct task that’s related to the parent view without taking them away from their current context.
A sheet appears as a card that partially covers the underlying content. The card’s top corners are rounded to visually distinguish it from the parent view.
Similar to your example, the parent view is still visible in the background.