No, It isn't equivalent. What Micnax and Element are saying is that completely restricting a specific class to make a map balanced is the problem. What you want from any map is balance with all 9 classes so that it can be played properly without the use of class restrictions.
Limits are different because they don't completely restrict any class, only prevent class spamming; which is in itself an inherent issue with any map when a game contains turtling classes like the engineer.
If a map is so open that you have to completely ban snipers, well, there are quite a lot of other issues as well. Think about things such as the wrangler, soldiers, scouts. Such a big map would not be just unbalanced with snipers, it would just be unbalanced period.