Not for everyone though and not always
This is why I stopped doing tricks. I work on sites for other people, bricks and mortar businesses, and get paid for doing something where I've made my best-educated guess that I'm doing good (and more importantly, not doing something that can do harm). I don't work on domains that can be discarded.
There is no more valuable thing than your own personal experience, but you do need to make sure that you conduct experiments to test only one thing at a time if you're going to get insight as to the merits of what you're doing.
I think you've convinced yourself this works, even though you've stated that you've seen no changes as far as Google is concerned when you've tried it yourself.
In my experience redirects at a domain level are counted instantly. That said, I've only used global 301s when moving domain with shared ownership in GSC to preserve existing traffic and rankings (something Google endorses) so my experience there may not be applicable. Maybe you need to give it more time. But, to be satisfied you can track cause / effect you'd need to down tools on this completely, wait a few months then check back. Or, you could try only more of the same: buy some more domains, build a bit of content on them, redirect them. If you do anything else you won't have any insight you could rely on as to what has produced results.
You've stated you've seen this work on other sites. If you were actually privy to those experiments (i.e. you know the webmasters involved) and can be certain no other work was done then you could be confident that an increase in rankings / traffic / pages indexed in Google (and NOT better Ahrefs metrics) was attributable to this. Then you could ask yourself why it worked there and has not (or has not so far) for you, and end up with some actionable insight.
However, if you've seen that there are domains doing well in Google who have this in their profile, that's not proof that it's helping them. They could be ranking despite this. It could even be that every link you can see counts for nothing and the domains are ranking from domain networks that are invisible to anyone but Google.