The contributions of the amp to the overall tone FAR outweigh the contributions which are provided by the guitar or any of the individual ingredients which went into building of the guitar.
Here's the rule... (which I suspect you already know)
You can take a great guitar and plug it into a crappy amp which will result in a crappy sounding guitar.
Then you can take a crappy guitar and plug it into a great amp which will result in a great sounding guitar.
On the macro level, this is all true, hence my initial post that you quoted. On the micro level, things become more nuanced, and the 'rule' becomes something of an oversimplification.
Sure, amp has a bigger impact than the guitar, but beyond that, the guitar still matters a great deal. The truth is:
1. A great guitar into a crappy amp is crap unless you're playing very quietly and super clean, in which case, the great guitar still sounds better than the crappy guitar.
2. A crappy guitar into a great amp sounds better than a crappy guitar into a crappy amp, but a great guitar into a great amp sounds better than a crappy guitar into a great amp.
This, of course, is why we spend lots of time seeking out the right nuance in the tone of a guitar, its pickups, its cable, and so on, when choosing one to play. It's why a single coil bridge pickup still sounds different into any amp than a humbucker into the same amp, or a hollowbody sounds different from a solid body.
In other words, if you want the best tone, don't compromise anything.
Now, of course, the operative question becomes, what's the best tone?