In a pre-IPO company, VCs and other investment groups consider unaccredited investors to be a liability, and they'll either give worse terms or no terms. If you're worth a million bucks the SEC considers you to be a grown-up and that you'll ask questions rather than being spoon-fed data that can help you protect your investment, which takes away a bunch of scenarios where you can litigate.
I worked at a company that turned out to have an unaccredited investor. I didn't hear the details but they had to 'fix it' before the VCs would move forward with discussions. (They still didn't get the money.)
GP's implication is that if you have a million bucks you can get (are?) accredited, which will give you access to private shares. I've heard this too, but I couldn't tell you the details.