Conclusion:
I expect multiple technical fouls, possibly ejections and Blazers covering the -4 spread. (If I'm not mistaken bookies valued first two home games at -2.5 and now is -4, that is almost 2x and I don't think they are trying to trick us, but rather objectively pointing out which team is better).
I agree with the conclusion, the line is fair since Blazers are up 3-1 in the series and they pretty win convincingly against the OCK.
Closing the series is hard but Blazers here needs to prove they can as they are up to a big challenge once they pass the first round, however we can't say that Blazers would win easily in this game, OKC can win and they might bring this back to their home.
For OKC bettors, moneyline is good as it has better return, and if a sportsbook offers at least -3 for OKC, that would worth a take with a sure x3 odds.