Some people say you do, others say you don't.
I just did a 4.5 Rubicon Express on my '98 XJ, and I needed one. There are guys on NAXJA that still don't believe me, but I took it to 3 different shops, and they all said that I needed it, and the geometry would not have been correct wit the stock pitman.
I trust the shops over the internet.

Especially when one of the shops was a specialty 4x4 place, and another specialized in front end work.
You can finish the lift and check the steering when you're done, and if it's not working and you're getting bump steer, you can order the larger drop pitman at that point.
I think my larger DP was around 100 bucks, or thereabouts...