I really don't think that's true for high-level professional players. Sometimes, yes, it's difficult to immediately count exact units compositions. I don't think professional players are getting confused by unit designs or finding it difficult to identify low-health units. (Don't pros play with all health bars on?)
It might be "unfair" for some almost purely number-based confrontation like a phoenix-versus-phoenix battle. But are we really that impressed by testing which human happened to be better at estimating the number of stacked phoenixes? To me, that's not what's interesting about competitive Starcraft 2. I'm more interested in micro, like pulling back injured units, or choices like "it makes sense for me to force us to trade out our phoenixes right now even if I lose the battle."
It might be "unfair" for some almost purely number-based confrontation like a phoenix-versus-phoenix battle. But are we really that impressed by testing which human happened to be better at estimating the number of stacked phoenixes? To me, that's not what's interesting about competitive Starcraft 2. I'm more interested in micro, like pulling back injured units, or choices like "it makes sense for me to force us to trade out our phoenixes right now even if I lose the battle."