If anyone can make the trainwreck that Jade is, work, it's SonicFox.
He never said Jaded was broke, not seriously, at least.
Sadly I think he is being serious. I don't think she is broke, there are many things wrong with her but in that variation there is some things going for her that can be strong.
What he is saying is her D4 is free spacing and the +3 is free respect/turns once conditioned.
To Sonic this translates to Broke
I don't think she is top tier or broke. just decent in that variation with some strong tools.
But I don't think Sonic is using her to prove anything. From what I know about Sonic, he only uses characters he thinks has strong tools that he can exploit.
Cassie, Jax, Nightwolf, D'Vorah, and now Jaded for the pressure and range.
I'm willing to bet Sonic uses Johnny way more than Jade. I don't think Jade does the best vs the entire cast so he is gonna be picking Outtake JC the majority. He says Outtake is Top 3. He is literally calling Johnny the new Cassie since he got her Glow kick right when she lost it and he has a good D4 for spacing and amazing Footsie not to mention 9f mid forceballs.
I don't think everyone should automatically agree with Sonic on everything but he does see potential in characters before others. Remember when he said Kotal and Shao was good and can play the meta just fine in the first month? Everyone said Shao, Kotal where garbage. He did FT10's with top players beating them using those characters B4 patches. Then VideoGamezYo comes along with Shao making 4th only using Jax for a couple MU's.
Furious Pillow & Azeez as well as Quark all made top 16's using Kotal when he was bottom tier on every list.
Sonic also labbed up stuff I never seen the other top players use long before we see others use it in majors. Then Everyone criticized sonics TL and then he showed them new tech and all of a sudden Deoxys and others came out with Tier Lists deathly close to Sonics.
He clearly understands the game better than most.
But he has made wild claims before and is generally hyperbole about everything so its hard to tell when he is right and wrong. And many just write his word in gold Tablets.
I take his opinions seriously but always test it for myself and get several other high level players opinions before I believe it fully.