The old way is to do that to ensure it’s long enough to cross chain, nowadays this need to be avoided especially on the smallest sprocket where the derailleur may not have enough tension to stop the chain from skipping on the 11/10t cog.
No, to be fair I didn’t elaborate; with modern bicycles now running a 1 by transmission, it’s too easy to just plop the chain on without realising it could be a little too slack (even thought it held tension and it’s not rubbing on the derailleur.
The old way is to do that to ensure it’s long enough to cross chain, nowadays this need to be avoided especially on the smallest sprocket where the derailleur may not have enough tension to stop the chain from skipping on the 11/10t cog.