Urn's speed is changed when you hit a Holliday pad with 2 ap in it.

[YepNoodles]

If you have Urn and hit a launch pad with 2 ap in it the move speed gets increased even though it's supposed to be set at a limited speed.

 

[steventheeven3]

Despite patch notes being a bit confusing, here's what urn actually does:

• Disables sprint speed
• Gives slow Immunity
• Gives +3.5m move speed
• Caps max movement speed at 15m/s
• Gives +30/30 resists

This is implied in one of the recent urn changes but not explicitly stated.