Transmission oil should always "look" new. Probably never been changed, so plugs were more than likely tightened at the factory!
Transmission fluid was changed but I had my reasons to doubt it was filled with MTF-3, hence I wanted to put new one in anyway. We’re talking even engine oil bolt which must have been tightened to at least 100 Nm :S
I’m guessing most mechanics do it “by hand”
It can take more torque to unscrew a fastener that took to tighten it, especially after it has been in place for a long time - a bolt may get rusted in, but bolts can stretch over time and may need less torque, there is no stretch in a drain plug but the washer can stick and make it seem tighter than it is.
When I change transmission fluid I always make sure I can get the 'fill' plug unscrewed before I take the drain plug out, this is after struggling with the fill plug on some cars - don't want to find yourself in the situation where the oil is drained out and you cannot refill it
it is good practice to replace the washer on plugs when refitting them ( they harden over time and may not deform properly when re-tightened ) I bought a load of different sized copper washers years ago - but you can anneal ( soften ) both copper and aluminium washers for re-use but copper ones are easier to anneal - just get them red hot and drop in cold water - polish any scale off sealing faces with wet and dry paper on glass surface and can be reused many times.
The plugs do tend to get harder to undo the longer they have been left in, same with sparkplugs - the longer life iridium and platinum plus have a special thread coating to stop them sticking ( they are expected to be in place for 70,000 miles + ) the normal plugs are just passivated zinc coating which can get a bit hard to move if plugs not changed on time ( like the rear plugs on i-DSi which can be ignored and be in for many years ). With spark plugs though it should be hand tight and then about half a turn - just to seal the crush washer - or about 25 NM IIRC.
Remember if you have lubricated a thread it alters the torque value - ( which is why the 'hand tight + 1/2 turn may be better for spark plug ) and you should lower torque by 25% - so the thread of a drain plug is pretty much always gonna be lubricated by residual oil in the thread. so is the rated torque for a dry or lubed thread ? ).