Does anyone consider "ProPress" ( https://www.viega.us/en/products/innovations/viega-propress.html )  a compression type fitting?  

It is lacking the traditional ferrule or compression ring seen in all other types of compression fittings, and it is certainly not a flare or brazed connection.  I believe it is a pressed fitting as the name implies.  Anyone have any thoughts here?

Al, I would guess he's looking at Dental Air/Vac and if pro press could be used under solder or compression as allowed joining methods. (Guessing here)

According to Viega's approval documents they consider it a compression fitting. The copper is compressed around the gasket(O-ring). A very similar principal to a compression nut and ferrule, but an o-ring in stead of the feerule and the pressure from the press tool instead of tightening the nut. 

OK from what I can get from the WWW:

1) Pro Press is Good

2) But Shark Bit has this, in their specializations.

Design certified to NSF/ANSI 61 and ASSE 1061 product standard for use in potable water and hydronic heating water distribution:

Approved to be used underground and behind walls without accesspanels. o Designed for hydronic heating as well as potable waterdistribution.