I would guess that the 'belt and braces' top bracket has to be welded to the upright, and there are safety issues involved.
I would suspect that toe changes will still occur, but they would now be neglible. It would be interesting to have the toe change measured with the new spacer in place?
More to the point, I believe that at least two people forwarded design drawings and ideas to MMC quite some time ago, which are almost identical to the spacer now in production. I can't help wondering if they have received a letter of thanks and a free kit?