In reply to dinodinosaur:
The "reachiness" of routes is more relative rather than absolute. The probability of alternative sequences may decrease somewhat with grade but for most climbers it's only routes near their limit which may prove impossible.
Reachy low grade routes are almost always perfectly climbable by a shorter climbers albeit with a harder sequence. Mid-grade routes may still have effective but harder sequences for short climbers, although not always. However the hardest routes are more likely to end up being nigh on impossible for those under a certain height.
Also my impression is that the critical height where the symbol comes into play also does seems to vary, again with grade. On the lowest grade routes where I've seen it, climbers under 5'8" could struggle whereas on the some of hardest routes with it, everyone under 6'3" would have an issue.
In summary, it's completely subjective rather than objective. Reading comments on the logbooks here will often provide more helpful insights on specific routes but most times it's worth giving routes a try.
Post edited at 23:21