I did confirm with UA yesterday that this is indeed true. Originally I asked via chat on united.com and after 30 minutes they told me there would be a meal but it didn't seem like they were really sure so I went through Twitter.
UA:
At this time, our policy is still reflecting that departures 800 miles or greater are eligible for signature meals. ^AL
Me:
I'm asking if that policy is going to change in 2024. That's when the flight I'm concerned about is happening. Without a hot meal severed it isn't worth paying extra for.
UA:
Okay, I was able to ask the appropriate teams to find out more. It looks like next year they will begin implementing this change starting on Jan 1st. Hopefully this clarifies things. ^AL