Whew, just getting over a cold. Time to finish up a couple vids I was working on. Here's the first of a 2 parter - grappling and dragging in D&D
Comments
I'd add to your explanation/analysis that, since grappling needs contested ability checks, to engage in the grapple you need to roll *higher* than your target. However, if they later want to break free, you need to only roll *at least as high* as them to keep them grappled - on a tie, "the situation remains the same as it was before the contest."
So, there's a 5% higher base chance for the grapple to remain than for the chance to successfully initiate the grapple and since attempting grapples is cheaper than breaking them (one attack from the attack action vs. a whole action), this makes grappling even better.