When translating, a one-to-one correspondence between the various parts of speech is not always maintained. This is especially true translating between English and Klingon, because their syntax is very different. I would have no problem at all accepting Klingons have ridgy foreheads as a translation of vIl tlhIngan QuchDu'. Whether the course accepts it is another matter...
The course did have variations with "Klingon foreheads are" and "Klingons have", but did not have variations with "Klingons foreheads have", "foreheads of Klingons have", or "foreheads of Klingons are" which I have now added. It has a few different variations marked as a "best" translation and when you get a tile exercise, it will randomly select between those various "best" translations and you may be presented with any one of them as the one that it provides the tiles for. I can see how it would be confusing to decide the best way to translate it and then not be able to find the tiles you need for that exact translation. Sometimes you have to let your mind be more flexible with the tile exercises and determine if there might be another acceptable way to say the same thing with the tiles provided.