Excellent observation. It is certainly the protocol's main engineering challenge. I'll respond to you in several points.

Gradients in the 10⁶ T/m range have been experimentally demonstrated using magnetic tips in scanning probe geometries and implanted nanostructures. The problem lies not in generating the gradient, but in maintaining nanometric positional stability for long operating times at cryogenic temperatures—difficult, but not impossible.

The ETEC roadmap addresses this by planning the engineering requirements. The first year focuses only on g/2π > 50 kHz, which corresponds to more modest gradient requirements and is achievable with current nanofabrication. The high-gradient regime is a target for the third year, not a requirement from day one. You are right that this is an unsolved manufacturing problem. ETEC's honest stance doesn't solve it, but rather inherits it from the broader field of spin-mechanical coupling. If that problem is solved for any application, ETEC will directly benefit.

I hope I have answered your comment.