Once round the pattern or a repo to pick up pax is all I've ever been approved to do on Ops check flights.
IMHO, someone up the line is making an economic tradeoff. Perhaps an occasional accident/fatality is considered to be a cost of doing business.
The amount of test flying after maintenence should, of course, be related to the nature/extent of the work performed. In this case, reports state an engine change and control systems components replaced. In human terms, a heart transplant equivalent. More than once around the patch would seem to be in order.
In 45 years of flying, only a few anxious moments due to mechanical issues, but most of these on an early flight after maintenance, so I am motivated to see that its been done right.