Weird install to external drive internal boot drive space usage with upgrade

[deckard666]

I am just testing the water by installing Sequoia to an external SSD drive (I have an M2 Mini Pro) that I had carbon copied from my boot drive - all going fine with the install/upgrade to the external drive (an hour left) but I am noticing that my internal HD space is dropping minute by minute and is now down 20gb - why ?

Weirdly just looked at Daisy Disk and I can see it increasing Purgable Space in real time....Ah it did it all and I got the space back but couldnt boot from the external SSD so not worth the hassle

 

[bogdanw]

but couldnt boot from the external SSD so not worth the hassle

Apple says "plug your storage device into any compatible port except the DFU port."
https://support.apple.com/en-us/111336
But sometimes it boots from that one.