Holmes does not succeed because he is superhuman (although the stories are not without their action bits), but because he applies himself more fully than others, and prepares and experiments more thoroughly.
Is the number of steps important?
Well, it would be if one were attempting to decide between two suspects, one on crutches and one a runner, and the time of path traversal was known.
But by then, others (notably the ever-mystified Scotland Yard) would have already dismissed stair count as unimportant.
Seemingly insignificant facts in aggregate, my dear albertgoeswoof, a case do build.
Except....what if that's just coincidence? I mean The Times costs the same amount at a news stand as any paper right? So what if the kidnapper, who is so barely literate he doesn't read any daily paper at all, went to a news stand to buy something to cut the letters from and happened to pick The Times?
Hah. How's that for pedantry, eh?
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The implication is that Holmes perhaps had a brain that was particularly well suited to such trivia, and a habit of observations. With practice comes skill in making and retaining such observations.
Now, the stair example is indeed a bit much. I doubt holmes would have counted the steps in every staircase he saw (though then again, if one practiced making such observations....). But Holmes did enjoy throwing people off guard, so knowing the number of steps in ones’ own home might indeed be a useful tidbit, precisely since it would offer the opportunity to throw Watson off guard.
I like this relevant scene: https://youtu.be/IjrWOZby8s8?t=47s
Disclaimer: I meant this constructively in case it comes of wrong.
There are an infinite number of things you can observe about the world around you, and there are many many more things you will not see than things you will see. All the way from high society people relations down to individual quantum particle interactions, it’s mind boggling how much there is out there happening at all times in all spaces. It’s not possible to observe all of this and the tiny fraction that we do observe is minuscule.
Pretending that there is some profound way to observe the world comes across as obnoxious and cringe-worthy.
A Study in Scarlet
Knowing how many steps there are is useless information and wasteful to retain.