A lot of Mac apps compress like this. Not so long ago, it was pretty common to download a 3-400mb dmg file that decompresses to a 1.5gb app package, for example.
But that's just "noticed", I definitely haven't paid much attention. And don't have a mac nowadays, so I can't go check my hard drive now.
Localization files compress well, compiled code compresses well, repeating assets (@1x, 2x, 3x) and the pair of binaries in a universal app (x86_64 + arm64) do too, etc.
Ah, and dmg compression is just LZFSE, zlib or bzip2, so pretty standard stuff as far as I understand it.