Exactly as is says, Link->Jump seems to be broken, or at least changed in a way that the current info on using Link->Jump is outdated.
For example, if this code is used in a script:
Link->Jump = 3;Link creates a shadow but doesn't gain any height.
Humorously, even this has no effect.
Link->Jump = 103;As stated, Mac build 1286, though it may have started in an earlier build.