Usually it's the other way around. By law normal investors have to be educated about all possible risks involved. Accredited investors don't need such information since they supposedly know those things already.
I can say if you don't check the 'accredited investor' box you never get the reports, in fact you never even get a message saying you won't get the reports.
If you're not an accredited investor, you're not going to be allowed to invest in anything that they require accredited investor status to receive information about.
Where's the law that says they have to require that? If it is a legal requirement, how do they ensure that you are actually accredited, because if they sent you the info and you had lied surely they'd be breaking the law?
iShares certainly has language in their website T+Cs which states that accredited investors can get access to information on the website which is not available to retail investors.
It is not ETF specific data. iShares offers some types of investments that are not available to non-accredited investors by law and offering information on performance of these investments would be a waste of time for both iShares and investors.
If ETF is offered to general public, its performance is available to general public, end of story.
There are ETFs today that anybody can buy that will only give complete information to "accredited investors". That doesn't protect consumers.