Everyone who voted for the Green Party were well aware that the intention was a Trump win and a Harris loss. Their people literally said as much.
Was it enough to cause a Harris loss? I don't know. I don't have enough information to know how many voters were discouraged. There were absolutely a ton of people on Lemmy talking about how the only "good" vote was a vote against Harris though.
So it is a problem. Just the matter of degree is unknown.