I think they’re two sides of the same coin. Contributions happen when someone’s motivation to contribute becomes higher than the barriers stopping them from contributing. You can lower that threshold, or motivate someone above the threshold; both have the same outcome. (Note: a full time salary is a pretty good motivator).
I think it’s useful. Hits both sides of the coin. Only downside is it’s a short-term boost while issue grooming is more efficient in the long run. But given increased availability now due to covid19, probably useful. I did something similar over in Hello there, I'm Axel! - #4 by smichel17