Well yes, it could be that there’s a full on integrity check behind the “check for updates”. Although I seem to remember having checked resource use during startup once and in this phase there was mostly network traffic and hardly any file I/O. So the question is: is it really necessary to transfer all the data that is being transferred just to find out if any of your install packages are not the newest available version (my naive idea of what “checking for updates” means)?
Then there seems to be that other minute right at the start. After clicking on the icon (steam, external shortcut) there is no window shown for about a minute. Do others have that as well? I often forget if I have started FS already and have to check in task manager - or end up with several instances.