Return of Reckoning

Hello, there is a potion named "instructor's boon" at the mounts vendor T1 warcamp, it reduce the xp gain by 75% for 1 hour.
These potion is only buyable at level 16, is that encourage the twink high ranked or not on the T1 ? It is better to have it only buyable to the level 10 characters only and not for the most high T1 rank characters ? A risk that could happens, it's to see a large amount of twinking who kill the T1... ?
I think players who want stay a little bit more on the T1 (or other low Tiers) for some good reasons must accept a power compromise and you ?

The potions are for reducing XP for mid tier toons,hence R16+.
T1 ends at R15.

Ok thanks reply and drive me out of my error, I was thinking the rank max on T1 was 17 because some low level characters are buffed to the rank 17 or 19 I have see on target indicator(rank 7 + 10 or this morning a slayer rank 19 on T1 RvR lake 15 + 4, a DoK rank 19, 3 + 16).