Not even close to being true. They encourage people to submit a schedule for consideration. It don't mean anyone who wants to can simply join up and start selling to the Government. If they did that the GSA catalog would be full of scam sites like MEXP.
I am responsible for my company's GSA Schedule. I can assure everyone it ain't as simple as dropping them an email. In fact, it is long and painstaking.
But what the heck do I know ... I've only been responsible for a commercial GSA Schedule since 1999.