Even if he didnt wore them he d still get say 20%
There is a possibility that either you were slow or he is not being honest or he Dced or died somewhere and was ressed by someone else without you coming to know of it. To make sure that they doesnt lie about EXP, Join some random guild and get yourself taxed at 50%. This will not affect your leech. The 50% that you get will now be 25%. The other 25% will go to that guild. Note the guilds exp score before you start and see it after you finish. Subtract the starting number from the finishing one.
Double the result - thats the base exp your leech gets. Add 70% more exp to it - Thats how much he should get with your leech intensive gears.
Note: 1% of trans 98 lvl is 3M exp points