Calculation are in the editor, but your computer is still processing them locally. Google Sheets is the same way when you have the sheet open. Your local resources are used to perform calculations.
Calculations don’t happen on the server. I’ve had heavy apps spin up my cooling fan when there is a lot to process. Mostly this has happened to me when I’ve created relations to a few thousand rows that rely on computed columns to compute on all of the related rows before the relation can return data. In some cases, it has crashed the browser tab, so I know it’s possible if you are making it work through a lot of data. If it’s happening on multiple computers, then it’s probably not an external source, but something with the structure of your app and maybe some inefficient relations. Windows Task Manger would confirm if chrome is using up resources or not. Chrome also has it’s own task manager as well to see which tabs are using resources.
As for my mention of loom, I wasn’t referring to the 5 minute limit, I was referring to the fact that the time paused several times in your video, which would indicate to me that the computer is working extra hard and using up all available CPU and/or RAM.