Yes, it absolutely must be. The top section must be reinforced with a strut or steel angle iron that runs all the way across the section.
This needs to be done because garage door openers pull straight back before they pull upwards causing the top section to flex a little bit each time it is opened.
Over time your top section will bow if it is not properly reinforced. Not reinforcing the top section will also void your warranty.
If you need a garage door opener installed at a great price and live in the Cincinnati or Northern Kentucky area, give us a call for a free, no-pressure estimate.