This is absolutely not true. Broker-dealers and brokerages routinely credit clients for execution out of line with the market. Schwab does in fact give price adjustments for slowly or incorrectly handled orders.

The reason nobody will be compensated here is due to two things,

(1) There is no way to determine what a fair execution would have been, since clients couldn't submit orders in the first place.

(2) Clients will adversely select their losing trades for corrections and this would bankrupt Robinhood in about five minutes.

Source: work at a wholesaler.