When I did my wetsuit testing years and years ago, I was able to talk with many who designed wetsuits. Almost all said that forearm panels were a cost of entry for the highest end suits but did nothing to make a suit faster and often made a suit slower.
I was sponsored by a wetsuit company years ago. They said "hey we're sending you the fastest wetsuit we make." Imagine my shock and horror when I saw their suit just below the top of the line suit. But then they told me why it was faster. One thing it didn't have was forearm panels.
Now if you prefer N=1 data.........Idk if it was bc I was in excellent swim shape or the suit was fast or a cmobo of the two, I lead out of the water, overall I may add, at a few races from sprints to half's in that suit. At the 70.3 WC exited in the leading group of 5 for the 30-39 wave (yes this is when they sent age groups off in 10yr increments).
I tend to still buy wetsuits that don't have forearm panels bc I've not seen anything to suggest that they've changed much in the years since then. ymmv
Brian Stover USAT LII
Accelerate3 Coaching Insta