Bannerman doesn't work with allies (even when they have it)

I use banners and I have been enjoying the effects of "Bannerman"

My teammates on the other hand have the same passive node "Bannerman", the buffs from the banner do not linger on them.

It clearly says "Banner buffs linger on you for 4 seconds after you leave the area" It does not state that it will only work on the caster.

Was that the intended purpose?

If so, can you change it so it works with allies as well? or make it work for them when they annoint it too.

Please and thank you