Things that seem very weak, but a doctor tells you aren't, are not "weak" in the medical sense of the term. The very fact that you feel weak is a great sign that you aren't. In the medical world, a pencil neck geek and a weight lifter are both the same "full strength". The point is you can use your muscles to fight gravity and resistance and win. They do their thing. That is the defintion of not weak.
Weak lips/cheeks causes sounds to come out wrong, people around you can hear the difference (you feel like you're doing fine, generally). They also cause drooling and drinks dribbling out of your mouth uncontrollably.
Weak tongue/throat cause you to fail at swallowing in some way. It doesn't just feel hard, or even slow, something doesn't work. It causes hacking coughs when you drink, the food doesn't leave the back of your mouth, you choke on foods, stuff like that.
Chewing weakness doesn't feel like that, it feels like the food is rubbery, the pasta is al dente... etc. You end up swallowing a lot of whole food.
That isn't anything like a complete list, but it should give you the flavor. Motor neuron weakness doesn't produce feelings of weakness, it produces failure, which you usually blame on some outside source at first. I know your next question "but what if this is a minor version/early/first step/etc?" As a PLSer, I have gotten to linger in the early stage for longer than an PALS gets to. It still doesn't feel like weakness, although with UMN, a lot of pain can be involved. But the pain comes if you use it or not... spastic jaw is hard to miss, it is like having it wired shut and only chemicals unwire it. You are just doing your thing one day, like singing in church, and you reach for the high note and nothing comes out. You yawn, and there is silence in the middle. Nothing feels wrong, but you can't do something you could before.
Last winter, I met my speech pathologist. She did an exam, and measured serious tongue weakness. Before that day, I didn't know it was weak at all, let alone clinically weak! I felt normal, but to an objective medical professional, it wasn't dong what it was supposed to be doing. It didn't move food between my teeth, didn't gather it for swallow well, and never finished the full swallow of food. No swallow of mine was actually getting all the food out... it turns out that the end of every swallow of food was just sitting at the back of my mouth, waiting to be breathed down. Yet, I thought I swallowed fine most of the time, and was just hacking occasionally on liquids. I felt fine. I still feel fine, and it is hard to remember that I'm not.
It seems like, with the motor nerves, that once your brain has sent the "do it" signal, it just feels satisfied that it's done. So weakness doesn't feel like anything you'd imagine it would. If anything, you feel like you've given it your normal force... you don't feel too weak to open the jar, you feel like the jar was tightened by a giant and curse the manufacturer.
But it seems your doctors have already told you that you don't have neurological symptoms. You don't believe them. You don't believe us that it doesn't fit the experiences of MND. Who will you believe? A speech pathologist? Go to one! They are bulbar area experts. Otherwise... you have to see where Joel is coming from.