I never heard any of that, so I guess the "mesostics" I've written don't qualify under that definition. But it doesn't bother me. I think those additional constraints are silly and pointless. As it is, I've done many variations on the mesostic concept. For example, I have poems that don't line up the letters but spread the blank letters throughout the poem for children to fill in. They then have to put the letters in order to spell out the word that is also the solution to the poem's riddle.
For me, what's important is that the poem also be good if you scrap the mesostic angle and just present the entire poem in normal typeface that doesn't highlight any letters. One of my mesostic poems was published in a children's anthology and the editor just published it that way, stripped of its mesostic character. The mesostic part is sort of just added fun and shouldn't be integral to the poetry itself. I had another that was published with the mesostic word running down the middle in an obvious fashion, rather than left blank as I contempleted (the magazine is found in many libraries and waiting rooms, so the editors didn't want anything that encourages people to write in it and ruin it for others).