It would be quite a logical to think that, given that the wiki says "The key sac_scale= is used to classify hiking trails in mountainous areas with regard to the difficulties to be expected., and “use this tag solely on ways used for hiking, as it solves a domain specific need”.
That’s how I use it, as I had never heard of sac_scale outside OSM so the OSM wiki page is all I have to go on. I don’t take the “mountainous areas” part entirely literally if I am mapping paths outside mountainous areas with an equivalent level of difficulty, e.g. along the top of a cliff. But I have always assumed that it is for paths used for hiking.
So as I map it, there is a meaningful distinction between paths with sac_scale=hiking and paths without sac_scale. Roughly speaking I use sac_scale as a hint that you might want to prepare a little bit more than for a walk along a sidewalk or in an urban park, for a variety of possible reasons (rougher surface, more isolated, steeper, needs better footwear than beach flip-flops etc etc).
If it turns out that sac_scale=hiking could apply to any easy path whatsoever, implying that sac_scale=hiking conveys no meaning at all as it’s the same as no sac_scale tag, I think I’ll just give up.