I’m going to guess it has to do with your settings in illustrator. Different programs each have different settings that are needed to save SVGs correctly so they don’t resize when imported into the GUI, and this is the one for Illustrator. And this is a very common question and if you want more details as to why etc., a quick search should bring it up. If that doesn’t help, let us know and I’m sure an AI user will chime in.
Here’s a more comprehensive listing of other programs just in case.
