I have a question about intel cpu microcode update

After a little research i decided to make a cpu microcode update but my mind is some confused.
I used latest linux cpu microcode and microdecoder program to extract right cpu microcode https://downloadcenter.intel.com/dow…code-Data-File

After extracting right microcode file i compared the two files.

One is cpu microcode that i want to update and other is current cpu microcode(I used AMI Uefi MMTool to extract cpu microcode).
You see the sizes are different.
But after integrating the latest cpu microcode to bios with mmtool the bios size with current bios size is same.
So i think why the sizes arent matching when comparing the microcodes can it be a problem ?also like linux is windows too using latest cpu microcodes ?

Yes, but the "Size on Disk" is exactly the same.

The complete size of the BIOS file should never be changed (not even a little bit, otherwise it will not work). It has to be always exactly the same.
If you replace any module by another one with another size, the BIOS tool (here: the MMTool) will compensate the size difference by customizing the compression.

why important is not size instead size on disk