So why does everyone take sides on this rule and consider it useless at the very beginning of the discussion in the forum, causing the discussion to be fruitless and not continue its process?
Because filtering actually slows down the search, no matter how you look at it, with zero benefits (because the filter itself has zero impact on the likelihood of success).
If I were to filter, the first thing I'd do is search the key in the regions where the filter matches, to make sure it's not there. And after that, simply remove the filter itself, since it's irrelevant to have it anyway and simply slows down the process. This way, you get a win-win: peace of heart that you haven't missed the key, and zero efficiency loss.
Most "filters" around here are so naive that they don't even consider the fact that they cover 0.0000001% or less of the total space, so this is why they are better off with the above strategy.