Siege Engine in 19th printing

[Gryphon]

Hello!
I'm currently trying to figure out how new rules and cards work. My question is about Siege Engine:

Originally Posted by Munchkin Change Log

You can ride in the Siege Engine at the start of combat. It does not count against Big items in play. If you do use the Siege Engine, you are -1 to Run Away.

So (how I see it) Siege Engine is like Casting Couch now — at the start of the combat I must decide whether I use it. If I choose to use Siege Engine, it stops to count as Big item, so... And this is the point I don't catch. What is a purpose to have one less Big item in combat if I can't play another one (since I am in combat and can't change my gear)?
Or maybe this ruling says that it never counts as Big? So the caption "Big" was removed?