It’s not really that they made it have more hydrogen bonds, they made it longer and therefore more hydrogen bonds. It’s like having a piece of velcro, and then using a bigger piece of velcro. Yes, the bigger velcro will be stronger. The AI was mostly used to design the scaffolding of the velcro.
They didn’t test whether it’s biologically functional (though that’s not really important if you only care about biomechanics).
Though the tintin protein is already absurdly huge, and I’m pretty sure that the time it takes to translate it is longer than the division time of a(n average) cell. And these scientists made it even bigger (or rather, one domain of it even bigger and didn’t make the rest of the protein).
Yeah the paper seems more like a material science paper than a biology paper. There was no test/simulations/discussion about biological function; similar to DNA computing/data storage, it’s mostly interested in the properties of the material than how it interfaces with pre-existing biology.
They did optimize for foldability, and did successfully produce the folded protein in (standard bacterial) cells. So it can be produced by biological systems (at least briefly), and more complex proteins had lower yields.
Their application they looked at was hydrogels, and it seems to have improved performance there? But functioning in biological systems introduces more constraints.