im somewhere in the middle.
ironically, if the car has been well looked after and isnt overly dirty then you shouldnt have any issues.
if the engine is in a poor state then you could have a fair bit of crap loosening all at once which could cause issues.
another option is a diluted flush run for a little longer followed by full oil change.
One thing i was thinking, is that the oil pick up pipe is something to consider after a flush.. but as this is a sump off job most wont be looking to do this.