I don't know much about app development, but I was curious and downloaded the Albert Heijn apk for ARM64. Inside the apk, the three largest entities are:
- libflutter.so 140 MBytes (flutter, obviously)
- flutter_assets 29 MBytes (this is a directory. The name is a bit misleading because it mostly consists of AH-specific icons.)
- libapp.so 20 MBytes (also related to flutter, I think)
There is a 640 KByte json file in the assets that stores an animation in base64 format. Now you know what the CPU and storage resources of your devices are used for nowadays...
So it seems flutter by itself takes 200-ish MBytes. Flutter alpha is 2017 according to https://en.wikipedia.org/wiki/Flutter_(software)
Mystery solved it seems