The 10 ft passage was a staple of the original game, as they used 10 ft (or 100 ft outdoors) as the standard grid size. However, spacing was much closer to 3 ft per human, as a front line typically consisted of 3 characters. I'm not certain, but I assume that's because that's what it was in miniature wargaming of the era. I do recall in 1E they had a required area to use certain weapons (e.g. a greatsword required at least 6 ft around you to swing properly) which impacted this. I think this is a far better system, as it also remove the "moving through other's space" situation, since you just can't do it.