no country told (down under?) parts and manuals and things vary all over earth.
well they did not lie to you, as it would damage the pump.\
but I see you are reading the wrong manual..
learn that systems of many kinds vary by
model or submodel or version even not known by you.
some even vary by build dates. or from upgrades
ask them only or bad things can happen.
Pentair Intelliflo Variable Speed Energy Efficient Pump VS+SVRS 3.2kW 3HP Max 230V
swimming pool or spa? or what? not told, (all of it)
nobody knows what you have there, for sure huge pools.,
all piping valves etc.
why not call for a real service tech>?
if down under ask them (Australia)???? not told
https://www.pentairpool.com.au/en/185/Home/Products/Pumps/Filtration-Pumps/-/intelliflo-vs-6
this manual contradicts you , per page 2
3:Use a check valve in the discharge line when using
this pump for any application where there is significant
height (head) to the plumbing after the pump.
4.Be sure to install check valves when plumbing in
parallel with another pump. This helps prevent reverse
rotation of the impeller and motor.<<< damage.
not told the application, wow, gee some pumps are below grade
of pool, and is called HEAD,
and with any far distance up, the check valve keeps the pool for draining to the pump area during service.
(the same true on suction side a pump down to a deep well
losing prime.
NO APPLICATION TOLD at all no real answers possible blind