Not sure. I have an X200 and it's AC adapter jack is not attached directly (as in soldered) to the motherboard. It is actually separate from the motherboard and IIRC uses a pigtail connector of some type to attach to the motherboard. I found this extremely reassuring! Mine does wiggle a little but I'm not worried as it will be attached to the motherboard no matter how much it wiggles.
Here is the hardware maintenance manual if you do not get a solid answer soon and congrats on the X220. X220 HMMEDIT:
Look on page 86 of the HMM. It shows how the AC/DC connector is attached to the motherboard.