Simply tried the support of crystal on windows and found
Linux and Windows handle memory very differently and also report it very differently. I cannot go into details because they elude my scope of knowledge, but base line is that one of these numbers is an apple and the other is an orange. You cannot compare them directly.
Regarding executable size, I presume the linux binary might be dynamically linked while the windows one is statically linked? That would mean the latter includes all library functions directly which naturally makes it much bigger.