I think I'm following what you are pondering and saw similar patterns with my DD when she was a baby. Even before she walked she was kicking and throwing balls. She is also a little perfectionist so her walking was grueling for us. She was early on sitting up (Started at 3 months and was leaning back balancing with her feet in the air by 6 months) but when it came to walking she would cruise with no problems and insist on someone holding her hand before she would step away from furniture. But the minute she was confident in her walking she let go and never looked back. She practically started running soon after. But in all fairness, I found DD's gross motor skills on the average side compared to her fine motor skills and verbals so I didn't pay that much attention to gross other than the fact that she wasn't behind and she wasn't. She officially started walking by herself when she was 14 1/2 months but could have probably walked at age 12 months if she wasn't such a perfectionist.
I have noticed during the past year during her 2 year age that she has great eye hand coordination. She is able to use a baseball bat and hit the ball when thrown to her and usually connects with the ball at least 70% of the time which seems impressive for that age if I consider most kids in Kindergarten do T-Ball with a stationary ball. She also has great control over a soccer ball and can throw tennis balls great distances and with great control. But I suspect this has more to do with how earlier she started doing these tasks (around 6-9 months).
I will have to ponder your analysis to consider if I have more examples for you ... I'm sure I do because what you describe just doesn't seem abnormal in my world anyway. I think my problem is it wasn't so much a 'trail run' as she worked on the first stage but more of this is the task I want to master and this is what I'm focusing on, if that makes sense.
