It can. This means in terms of downloading and processing assets, the Tealium tag is lower in priority. The reason to do this typically is if you want to prioritize the user experience as much as possible, such as images and scripting related to that. The possible downside is that your tagging fires a bit slower. It's really a balancing act. Tealium's best practice of being at the top of the tag is where we consider the best balance to be.
Just to add to this, we've had cases where moving from the bottom of the body to the top has improved tracking by approximately 10% on HTML pages with a lot of assets on them. If your pages are relatively small, chances are that the difference won't be as high as this particular case, but on larger/longer pages, it can be a bigger issue if utag.js is buried at the bottom.
Check out our new Swift integration library for iOS, macOS, tvOS and watchOS: https://github.com/Tealium/tealium-swift with updated documentation https://community.tealiumiq.com/t5/Swift/tkb-p/swift.
One area which can really be affected is order confirmation pages. As with any vendor tags, the lower down the page it is the longer it takes to fire. This means if a user hits the order confirmation page but leaves very quickly before the Tealium tags can fire - you will be missing orders from your vendor tags (e.g. analytics tools, affiliate vendors).
For this reason, I would strongly recommend putting it as close to the top of the body as possible at least for order confirmation pages.