i agree. the whole thing you have to realize is about how distortion and compression work. generally an amp introduces both to the signal. The nature of compression and distortion is affected by the dynamics and frequencies fed into them. So EQ'ing before the amp distortion will alter the nature of the distortion. distortion effects and EQ's can take advantage of that, making the distortion more or less fuzzy, or emphasizing frequencies that make the tone smoother or more biting, etc. a mod effect can do some crazy stuff before distortion, as it tends to cause the peak frequencies to change over time - so you get both the mod effect and variations in the distortion tone. EQ's after the amp act the same as amp controls - they adjust the final bass/mids/treble, etc. in the tone. I use EQ's in front to "sculpt" the distortion tone, and behind to dial out unwanted frequencies or boost/cut some aspect of the tone. for instance, boosting bass in front the amp will make distortion more muddy and farty but behind the amp just makes the tone really bassy and boomy.
a compressor before an amp distortion will cause a stronger signal to hit the amp, even as it sustains, causing there to be more distortion, even on sustained notes. in contrast, a compressor after amp distortion will cause less dynamics and more sustain, but the distortion tone will not be affected. So if you play soft, the note will be easily heard and sustain longer, but it won't be as distorted as when you are picking the strings with all your might.
shifting pitches after distortion can sound a bit digital compared to in front of distortion. but keep in mind distortion distorts differently on intervals vs single notes. For smart harmony, you often want to sound like two guitars playing in harmony, rather than one guitar playing intervals. then you want the smart harmony behind the amp.
wah is traditionally in front the amp, but if you want the rage against the machine bulls on parade sound, put it behind the amp.
volume pedals before the amp basically act like a guitar volume knob - it controls how much distortion you get then it starts rolling off volume, similar to the amp's gain knob. behind the amp, a volume pedal linearly (or something like that) alters the final volume without affecting the amount of distortion in the tone.