It seems that some people, who haven't built frames with them, misunderstand the difference between 135QR and 142TA dropouts. In order to help explain how the dropouts are attached to the stays in the exact same location on both, I have taken some pictures of one of my frames that was built for 142 thru axle.

This recessed slot is the only reason why thru axle hubs are 142mm wide. The slot is 3.5mm deep on each side, so the hub end caps were widened by 3.5mm on each side to allow it to self locate in the dropout, similar to a QR dropout.

The distance between the inside faces of the dropout is still 135mm, so the dropout attaches to the stays in the same location and the stays are the same width on both 135 and 142.

The distance between the faces of the dropout slot is the only thing that is 142mm wide. Obviously the outside face of the axle hole is wider, but that does not affect the placement of the dropout on the stay.