And I think I found my answer in this closed issue in choosenim: [https://github.com/dom96/choosenim/issues/128](https://github.com/dom96/choosenim/issues/128)
It appears that if it finds a gcc 32 bit compiler, choosenim will download the 32 bit Nim compiler. I did have in my path only the gcc 32 bit compiler so it was expected behaviour of choosenim.
