I have never seen any rule about channels except that channel 10 is for drums. The only time I can think it would make a real difference is if your synth uses "performances" (which is another way of saying that the patches and effects are pre-assigned to each channel for that "performance")

Patch settings in a performance override the patch settings in a sequence. So, If you had a bunch of performances set up and wanted to rapidly change patches & effects in that way, it would make sense to ensure that your midi sequences conformed to the same instrument lineup as the synth performance.

In other words, if all your performances had a guitar patch on channel 1, a bass patch on channel 2, a keyboard patch on channel 3 etc, you'd want the sequence to be the same... otherwise, each time you changed performances, you'd be sending an inappropriate patch to all your instruments

It is hard to get too obsessive compulsive about using the same channel only for one instrument as a rule, because each port only supports 16 channels, but there are wayyy more than 16 possible instruments

In summary, if you are NOT using performances and you ARE setting the patches in your sequence using the patch select dialog box, then it doesn't really matter what channel each instrument is on. You are programming it, so you can make it however you want.

https://www.dropbox.com/sh/ey71h8ep047758h/AAC12jNM0Hz9Q8zsh5iDeqNHa?dl=0