Condensate pipe termination

[kasser]

Getting confused with how to route and terminate condensate pipes.
My gas manual shows a diagram with the condensate pipe connected upstream of a washbasin trap.
Baxi's manual does "not recommend", in caps, to connect upstream of the sink and its diagram shows the connection downstream of the washbasin trap.
Intergas on the other hand says just dump the condensate tube in an open waste pipe. No need for any trap unless connected to a soil pipe.
Ravenheat's examples show the condensate connected upstream of the washbasin trap and state as much.

I know MIs must be followed but what's the logic here and why are the instructions so contradictory? They're all condensing boilers with internal traps, so no external air breaks are needed, that we can agree. I thought the condensate pipe had to be terminated such that flue gases could not escape in the room, so why do some manufacturers allow open-ended waste pipes or the trap after?

 

[ShaunCorbs]

if dumping a full sink you could in theory pull the trap out the boiler also seen a condense get blocked with food waste that was tee into the washing machine port of a trap

 

[Harvest Fields]

if dumping a full sink you could in theory pull the trap out the boiler also seen a condense get blocked with food waste that was tee into the washing machine port of a trap

The last bit happens all the time in social housing.

 

[kasser]

better stick it in an open waste pipe then, no blockage