There is currently a bug where a player is able to use the enweb ability when a card with convoke is in the hand. If any untapped creature is on the battlefield under this player control he is able to tap it for the enweb ability. That creature is then tapped for mana as it would for convoke. That mana can't be used to pay for the enweb cost but it is still added to the mana pool.
This can't be replicated with full control. only happens when using auto-tap.