I got that impression from the policy as well; that you can just change the phrasing in many cases:
Describing to the reader how people or things use or do something is encyclopedic; instructing the reader in the imperative mood about how to use or do something is not.[4] Wording can easily be modified to avoid advising the reader:
Do not give aspirin ... ⇒ The WHO advises against the use of aspirin
To re-use an example, you could give a description like this which doesn’t mention any other species or advise how to distinguish them:
That successfully eliminates all the other similar Melanerpes species, but it becomes sort of a logic puzzle for the reader to figure out which individual feature doesn’t match if they’re looking at an observation of one of those species. It’s much more intuitive to add another paragraph:
They differ from other species in that Red-crowned Woodpecker is very similar but is only found between Costa Rica and Venezuela, Gila Woodpecker has no red on the nape… etc.
But that might be over the line given that the Wikipedia articles for those species don’t include anything like that? When you get into more intricate ID challenges with multiple variables to compare, those comparisons are almost essential.