It is. Halting trades always produces winners/losers.

Retail investors are RH's biggest customers. They're diminishing their risk of suits they'd likely lose/regulatory scrutiny by halting buys. The SEC will more likely hit you for allowing pumps rather than preventing them.

It's absolutely not the same

Trading halts are at the exchange level and stop _all_ buys and sells

What happened here is some brokers/clearing houses prevented _retail traders_ from buying, but not from selling

Exchanges are able to decide what to halt (obviously since that's what they did). The SEC/class action suits are free to argue the issue, but the likelihood the suit will succeed is low and SEC intervention (beyond an opinion statement) is also low. In the investment space, retail investors are generally treated like children who need to be protected (that's what the SEC is mostly tasked with). RH will make the argument that it was protecting the children from hurting themselves and the SEC will likely go along with it (that's their assumption anyway). Fairness isn't something you generally see in trading.

How is halting trades the same as only halting buys? By halting trades it is implied selling is also halted.