Thanks, glad to hear you enjoyed!
As for your question, the game runs on something called Edge Webview2, which is the biggest reason for the size difference. In the x64 and x86 versions, it's bundled in which increase the size quite a lot, in the non-fixed version it is not bundled in and instead uses the version which is (by default) installed on your Windows system.
In some cases, using the non-fixed version will causes issues for some users who have an older version of Edge or have outright removed it.
Hope this makes sense!