Money market accounts have been around a while. Is Robinhood's account different because they are subsidizing it to hit 3% APR?
SIPC on the other hand is more relaxed because it covers less. It only covers when a member broker becomes insolvent and is unable to return a security to you that you own.
There are similar funds that invest in short term treasuries and often that you can write checks against, however they don't offer 3% and they're very transparent that you own these securities and are subject to the (very low) risk that comes with owning them.
Robinhood's marketing sounds a lot more like a standard FDIC insured bank account but they're saying it's SIPC insured instead, and the SIPC is confused about what securities they would actually be insuring
The question then becomes whether this is a good kind of move-fast-and-break-things a la early Uber breaking into an over-regulated market, or if it's defeating an important protection that consumers need.