FTOs IR Training
Notwithstanding the additional valid comments of cfb, I would question the wisdom of any FTO which would permit an instructor's actions resulting in potential additional costs for any customer due to their FI's inability to understand METARS / TAFS.
Any reasonable FTO would regard the cost of any such nitestop as wholly down to them, and meet the additional expenditure incurred.
IR training is expensive enough, without less then capable staff being able to exercise appropriate professional judgement as to when to fly for the benefit of the student.