Yeah I hear ya on the issue of being too rigid, luckily not the case here.
The rear part of these is fairly solid enough to support the arch without deforming - but the lighter material that you see the forefoot made out of is reasonably flexible, enough to allow it to flex with the foot. No problem roll onto the toes of the boot, they move fine for that, you could fold this in two if you really tried.
They feel about the right balance between support and flex. The fitting was done by standing (maybe sitting I cant remember) with feet on deformable pillows, then the insoles heated placed on the (somehow now solid) pads and feet back on top until set.
Anyway, this isn't an advert for that brand/type, I'm sure there are better systems. The point is that the it should be obvious to people with problem (or even 'normal' feet) why it's worth bothering with customs at all.
Let's look at the cost too..
Customs insoles price: 85€ (and the guy added some shaped foam behind heal of the liner for free at the same time).
Total cost: €140€
Why more?? Because I bought a pair of Gamechangers first. They are sat gathering dust. I paid out for them then had to get customs done anyway, they were literally a waste of money.
Not knocking Gamechangers particularly here, they will be ok for some people - just be aware of any aftermarket insoles limitations. And if you have difficult feet, don't be tight. It will cost you more in the long run.