+1 on the counter bore bits. I think the standard ferrule size is about 8mm - 5/16”?

prior to getting a drill press, I used a drill guide, but one that is a fair bit smaller than the one in the video.
It’s called a Big Vee, by Gator tools:
https://www.carbatec.com.au/v-drill-guide-metric

It will not allow you to go all the way through the body, but it is only about 5/8” high so you can get a decent bite in with it. Clamping it can be a challenge due to its size but I found a work around on that using some home made clamps to grip its sides. As you are no doubt finding with your guide, the majority of the fiddle in the process it getting it sited in on the hole and properly located.

I think your test piece is probably giving you a false result, even in the initial shot it looks very close grained and splintery so possibly not a fair test.

Practice a couple more times on scrap, find out what works and makes sense for you and then get set up for the main game.
best of luck with it, sing out if you have issues.