In all fairness to Rusty Wessel this could all be nothing more than a simple mistake based on a lack of correct geography. That, or maybe, just maybe, as Madness implied this fantasy name was made up to make these fish appear "new" and more desirable to unsuspecting hobbyists. Of course this can only be answered by Rusty Wessel.
The whole thing seems rather très bizarre to me. If these fish came from Lake Managua as Rusty apparently stated to CrimsonFrog, then the obvious thing to do would be to apply the current scientific name to these fish, which is Amphilophus labiatus. If he wanted to be really accurate, and add the collection location for the true purists, he could have attached "Lago Managua" to the name, such as Amphilophus labiatus "Lago Managua". Something that Jeff Rapps has been doing for years.
Again, where, how, or why "Laguna Yaxha" came into this is anyones guess, but clearly this is the name that Rusty Wessel attached to these fish, the why part of that can only be answered by Rusty Wessel. Either way, hopefully those that have purchased these fish will contact Rusty and inform him that there is no such thing as Amphilophus Labiatus 'Laguna Yaxha', and that Lake Managua is the Central American lake that borders Managua city, Nicaragua, where he now states these fish were collected.
If it was an honest mistake then it shouldn't take a whole lot of effort on his part to set the record straight. I guess time will tell.
