I think you are confusing "having skills" or "having experience" with taking the time to know the competition, taking the time to know the customer, being willing to send them to a completely different solution that you can't meet.
I'm not confusing anything.
If you change the thread title from "Why You Don't Get Advice from Vendors" to "Why you should maintain a healthy scepticism about advice you get from vendors, why you should engage with multiple vendors and why should verify all vendor advice with your own independent research" then I agree with you completely.
Mostly you are just pointing out all the weaknesses and caveats of vendor advice. That's all to the good, but that is not the same thing as saying you should never get advice from a vendor. Getting advice from a vendor is a great way to learn and a great way to help source new products and solutions. I'd advise all IT pros to get as much advice as possible from as many people as possible - and that includes, but is not limited to, vendors.
No it is exactly the same. You should never get advice from a vendor. Our company works the same as NTG, we are consultants. We refuse to become resellers for any product because that will taint our advice. This is why I do not identify our company as a MSP anymore, because most MSP companies are reselling something. This means they are not actually giving you unbiased advice. They will be giving you advice they makes their company more money.
True, that most will still work on anything, but they will always be pushing Dell over HP or something similar.