Here is a copy of the mnr regs re size limits.
A variety of size restrictions apply to some species and waterbodies (see Map, A, B, C, D or E ). Unless otherwise stated, size limits refer to total length , which is a measure from the tip of the mouth with the jaws closed to the tip of the tail, with the tail fin lobes compressed to give the maximum possible length.
For some waterbodies, the regulation may specify a size limit that is a fork length . Fork length is a measure from the tip of the mouth with the jaws closed to the central part of the tail fin (see below). If you catch a fish in a restricted size range, you must release it immediately. (See Tips on Live Release of Fish ).
Provincial regulations are established using the metric system. The conversion to inches has been rounded to one decimal place for the convenience of anglers.
You friend was in the wrong and I commend him for not complaining about it.
Personally if I catch a walleye that is close to the slot limit I don't even hesitate to release it. Just not worth the risk if you ask me.
I have had nothing but good experiences with the COs in this area thankfully and I commend them for the job they do.