-1 my rosh yeshiva has a vocabulary that could make your head spin. He has written many letters of recommendation for law school applications. They don't give those jobs to chimps. There are many rosh yeshivos that are both polished and worldly. Especially in today's world, being able to relate and navigate is crucial.
P.s. You would never tell by looking at my rosh yeshiva, frock and long white beard like the rest.
I'll make this point only one more time.
When a RY writes a letter of recommendation, he is thinking it should look like a haskama. I have known this person for many years when he was a student in our yeshiva, and he is a big talmid chochom and I was so glad to see this sefer that he toiled on and you will learn a lot from it.
Which is what haskamas are supposed to look like. But not what LORs are supposed to look like, even if written with every word in the thesaurus.
That is why you need to counsel your ry on what to write, if you are asking him to write. Tell him to make it long (page and half I'd guess), specific (one time in my lecture he answered a question that had been bothering me for years with a brilliant theory, etc), and earnest (sound like he thought about it and isn't just pushing out what he writes for everyone).