Can't a long-tailed keyword also utilize the short-tail keyword in a sentence?

Hello and thanks in advance. I'm well aware of the difference between the pros and cons of long-tailed vs. short-tailed keywords from an analysis standpoint of keyword validation.

But in writing articles: Do I have to end a sentence with a keyword to ensure I don't potentially limit it by inadvertently "turning it in to a long-tailed keyword" by simply using it in a coherent sentence?

No one uses a keyword as an entire sentence (maybe a title)... yet you don't want to supposedly "turn your short tailed keyword into a long one" according to my old boss. (or if a short tail keyword is 3 words, then technically we're talking about turning a shorter long-tailed keyword into a longer-tailed one).

Like, I wanted to utilize (yes it's a tiny niche) "how to build a cloud chamber". But if I write "How to make a cloud chamber at home" -- suddenly that's a longer-tailed keyword. But it's also just a really sensible way of simply working the short tailed version into a sentence!

I can see how, "How to make a cloud chamber without dry ice", is, yes, a more specific search that I could see google limiting to its relevance. But what about "How to build a cloud chamber at home"? Almost everyone asking how to build a cloud chamber is doing it "at home". Or if I type "How to build a cloud chamber and impress your friends" is Google not taking the shorter tailed version "How to build a cloud chamber" into account in these latter two examples because I didn't end the sentence with it?

What about as the title? Should I always title the article with just the verbatim keyword and nothing else? Or maybe only end it with the keyword and restric extra title words to before the keyword so, again, I'm not turning it into a longer tail?

The boss kept accusing me of turning keywords into longer tailed ones that won't be searched as much and the only way I know to avoid it is end the sentence with the keyword!

I can see how "What's the best paver sealer" is searched more than "what's the best paver sealer in Florida" and google may avoid showing that to a guy in Nebraska. But if I type "What is the best paver sealer to buy online" or "...for me to get?" -- is that turning it into a longer tailed keyword that will truly be picked up less than "what is the best paver sealer"?

The short version is contained in the long version (esp. when it's not limiting it per se like specifying location). It's just being used in a coherent sentence. So I get confused about application and usage, not what they are on the other end of the search engine.

Thanks for any light you can shed! Sincerely, Currently ending every title and sentence with the keyword to avoid turning them into longer tailed ones: Otter (Jeff)