An aeropress doesn't actually generate any pressure. It just moves a column of water through a puck of coffee like a percolator. You can buy some special add-ons for the aeropress that cause it to build pressure but it's really just for generating more foamy/crema brew and not getting a proper espresso shot out of it. All that said the aeropress is still awesome and a great way to brew coffee, it's just not going to replicate espresso shots.
Their point was simply that the high pressure attachment only creates the superficial appearance of crema, not actual espresso.
Your EK43's, Mythos Ones, EG-1s etc have steel burrs.
Source: I own and repair espresso machines as my hobby and for my daily coffee habit.
That’s certainly what I do. In the geek world though, they are going a lot lower. I’ve seen 6 mentioned and 7 or 8 is common.
There is also the effect of the pre-infusion which is a lot lower.
I haven’t explored this world, but there are plenty of die hard proponents of it.
Also, this project is about sophisticated temperature and pressure/flow control, something even many/most professional machines simply can't do. So I really don't think the person who built this machine lacks experience in brewing coffee.
Not very much pressure, but there is pressure
Given the notoriously grainy mouth feel of aeropress coffee, and the sheer joy I've had out of proper espresso made with even less-expensive home machines (e.g. a Rancillo Silvia, to say nothing of nicer home machines like Rockets), I'm utterly stunned by the weirdness of this assertion.
I wouldn't be more puzzled if you'd said the best you can do at home is a Mr Coffee. Dead serious.