I'll hazard a guess...
The reservation system has placed the symbol on the wrong 'Snow' Lake. Here's why I think that...
There is no canoe route or campsite or previous route on Snow Lake in the north end of the park (as you mentioned) however there are two campsites on the Snow Lake just a couple lakes past Hilly and Bluebell (near the west gate). Take a look at the reservation numbers.. Bluebell is 152 (campsite closed, hence the always red), Hilly is 153 and I assume this Snow lake is 154 when it was active - maybe one of those sites you book but don't pay for because its out of the park (like Killarney when you leave the park for a night and come back, they book you somewhere but don't pay for that night).
So I think this is the Snow Lake by the west gate, and the reservation system placed the icon on the wrong lake.