I remember discussion of the TVM there that indicated it isn't possible to collect tickets there as it only sells MR tickets. I don't know if this has changed since.
Edit: It was
this thread.
You can collect tickets from Liverpool South Parkway that have been booked online. The TVM in qustion is the only one on the Merseyrail network that allows you to do so. The TVM in question at LPY is actually branded as a Northern TVM though - even though Merseyrail run the station. Maybe this was not the case when it was first installed but I have collected tickets from it recently that I have booked online.
All the other TVMs at other Merseyrail stations do not allow you to collect tickets brought online, sadly.
You can collect tickets from Liverpool South Parkway that have been booked online. The TVM in qustion is the only one on the Merseyrail network that allows you to do so. The TVM in question at LPY is branded as a Northern one though - even though Merseyrail run the station. The discussion you provided the link to was about how other Merseyrail stations have TVMs but, as you say, only see walk up tickets (to travel to any destination, not just those on Merseyrail).
As per the thread you linked to, there is a picture to this TVM and a post explaining it is Northern branded etc. Sadly, many of the websites have caught on to this and some sites still do not offer LPY as an option.
Given there is only one TVM at LPY, would the ticket office (ran by Merseyrail) have to be able to print the tickets if the TVM was out of order or if there were any problems? I wonder how this would pan out in reality...