I had heard of this, but forgot about it.
But I suspect there was an earlier example of Wonder Woman getting her own cartoon solo adventures and, oddly enough, the connection is the Brady Bunch.
After the success of the Brady Bunch sitcom, as well as the success of the Partridge Family, the Brady producers decided to turn the Brady Kids into pop stars and had them churn out a few albums as well as performing some songs on several episodes.
This let them to get Filmation Studios to turn the Brady Kids into a Saturday morning cartoon series where they would perform their songs. They even recycled the Archies band animations, replacing the characters with the Bradys, but they were playing the Archies' instruments and had the exact same movements. They even replaced Tiger with a dog called Mop Top who was actually Hot Dog recolored brown.
A couple of Brady Kids episodes featured guest stars. The first was Superman (with Lois Lane), and they recycled the same animations Filmation had used years earlier on their Superman/Aquaman Adventure Hour. The next guest stars were the Lone Ranger and Tonto who were magically transported to the present by the Bradys' magical mynah bird (don't ask). Again, the animations used were recycled from Filmation's Lone Ranger cartoon of the 60s.
The next cartoon guest star was Wonder Woman. And this was before the Super Friends cartoon premiered, so it would be Diana's debut in cartoon form. Because of Filmation's track record of using recycled animations, it might be safe to assume this was true of Wonder Woman as well. Except the Superman/Aquaman show did not feature any Wonder Woman segment. Ironically, Wonder Girl WAS featured in the Teen titans segments, so she beat her sister to TV. Interestingly, the only other heroine featured was Mera in the Aquaman segments (though she was always being rescued). The first season did not have a Batman segment, because the rights were tied up with the live action prime time Batman series. Later, a Batman segment was added and Batgirl appeared in some. Interestingly, there was a Superboy segment, but no Supergirl. There was no Hawkgirl in the Hawkman segments. There was a Justice League segment, but they only used the heroes that had segments in the show (except Aquaman); Superman, Flash, Green Lantern, and Hawkman. No Wonder Woman or Black Canary. Maybe they made an exception for Wonder Girl in the Titans because they thought there should be more than 3 members on the team (they used Speedy in place of Robin, again because of the rights being tied up, so Speedy also beat his mentor to TV who would have to wait for a guest shot on the first season of Super Friends).
So my theory is Filmation did a sample Wonder Woman cartoon adventure for the pilot to pitch the series to the networks, but I'm betting some exec told them they didn't think kids would want to see super heroines, so that was that. But it would have left them with animation to recycle for a guest shot later.
I also suspect that the Superman and Wonder Woman guest shots on this show, as well as Batman and Robin's guest shots on the Scooby-Doo Movies were most likely the inspiration for the Super Friends and why the original junior Super Friends were just regular teens (Wendy, Marvin and Wonder Dog) unlike the later Wonder Twins who took their place.
Here's a YouTube video of a commentary on that Brady Kids episode with Wonder Woman:
https://youtu.be/aKWJBuB1760