Neil- I tend to agree but in rule books says:
"The player may use their Ranger’s movement abilities if they possess any, and may also discard Defender Cards with movement icons to move more than one location..."
That "and may also" is what's causing the confusion. I wouldn't think Jake could take his bike then ditch it for glider for combined 5 spaces, but doesn't specify that, in fact seems to permit it.
I agree. If you couldn't combine them, the rules would say so.