I'm a current robinhood non-gold user and they actually eliminated this restriction around 6 months ago. Now as soon as I sell a position I can buy my next with the funds from the sale.
Which they have branded the loan they give you until deposits and sales settle "Robinhood Instant". Since you are trading without settled cash in the account, I believe the SEC considers this a margin account.
Yes, I have this too. Robinhood Instant is a margin account, with the same conditions/restrictions as a Gold account. They loan you money in that settlement time window, basically