I read this some place a year or two ago...along with some pictures of fvcked up syncros. i can't prove to you why or why not because i don't remember..., but i can tell you the answer because that i do remember.

when you down shift and skip gear(s)...say 5th to 3rd, you can do it without harming the tranny if you can rev match. if you just drop the clutch going 5th to 3rd, more strain to your tranny.

when you up shift and skip gear(s)...say 3rd to 5th, you want the rpm to drop completely...to at least around 1000k before letting that clutch go. say you're going 60mph in 3rd and you upshift to 5th as you would to 4th...you're grinding your syncros. there was a picture posted on another forum of a grinded/worn off syncros due to skipping gears (up shift) and it didn't look pretty.

since then i don't skip gears when shifting up anymore. only rev match and down shift. my little advice from the readings is that just hit every gear because it doesn't take much effort or time to do it. go in order and you have no problems.