Being in the business as many years as I have been this is the first time seeing this type of mount.
Granted we don't have tile roofs here so that may be one of the reasons.
Retailers don't really care when it comes to stocking an item if they can make money, but the issue is this thing costs almost $70.
When your making $200 on a sale, $70 is something you just can't afford to give to the customer for free.
A retailer may choose not to carry this as it falls under the same policy as HDMI cables. I used to stock 6, 10, 15 and 25 foot cables.
I kept on buying the 25 foot cables but would never see them being sold on invoices.
Installers try selling them to the customer, customer would complain about the cost and we would give the extra long cables away for free.
Took away the longer cables from my installers, now everyone uses the 3 foot cords.
Just saved me a few hundred dollars per month.