I did a quick search here to find that Jefferson nickels have a +/-.18 gram weight tolerance. Found this 1940 nickel roll hunting and weighed it on two different scales. See results in attached pictures. This is nearly an 80 year old coin but could this be enough reason for it's low weight?
It probably started as a lower weight Nickel and then weighed less over time because of circulation wear.
I would say that yes it is probably slightly of of tolerance, but considering it is also worn I'd say it was VERY slightly out of tolerance. Probably .05 grams below tolerance when it was new.