The shim solves the problem when we lower the bridge or the saddles as much as we possibly can, but still we cannot bring the action low enough. Once we've added the shim we will need to do all the adjustments once more to bring everything back into harmony.
The inability to bend strings in the middle of the neck would seem to be more a problem with neck relief or fret leveling needed, for me. A guitar neck with a proper amount of relief and with the frets sufficiently level would not encounter difficulty bending under normal circumstances. Perhaps another item to checks to see if high frets can be pinpointed or if they are all unlevel as may be common on lower cost guitars. Fretwork is labor intensive and suffers on lower end guitars it seems.