assembly save as part

hi,

my problem: I receive files .step for PCBs and I convert them in .sldw files. they become assemblies with hundreds of sub-assemblies and parts. after, I was doing Save as -> .prt. I tought that the new file will be smaller and easier to manipulate. in fact, the new file(.prt) is 2-3 times bigger than the assembly. it is normal?

SolidworksAssemblies