just in case you have the box and want to skip this step, the IMEI is always printed on the box somwhere
Yes, it does: At least the cellular modem, as @nephros already pointed out.
People have been running into severe issues, when trying to use “roaming” abroad.
This step is supposed to avoid this.
I mean, the major point for me to use Sailfish OS is, that I do not want to feed the Google monster with my data.
There is no reason to feed Google with this information.
Actually this the reason, why I wrote this section of my extended install guide.
So if you run into issues to use “roaming” (e.g., abroad), “simply” re-flash to Android and do it all over again, utilising aforementioned guide.
Or just boot a LiveCD/DVD/ISO from a USB Stick and see if a different Linux Distro works correctly in case you don’t want to reinstall your PC or Laptop just because you need to flash your phone!