I never heard of that, so I did a quick google, and I found only this one video (and its for a x1 carbon) explaining to disable the battery within the bios, which would in affect fully power down the laptop
All of the other videos I saw just jumped in and replaced the SSD. I suppose it cannot hurt to turn the battery off, but if it were me, I'd probably just power down, remove the A/C power cord and open up the back. If you don't feel comfortable, then yes by all means go into the bios