I had a Rocket Retro RR50 and it never had any gain at all. It played like a JTM 45 .Your video now makes sense. It was possibly just missing the bright cap. At 7 on Volume 1 it sounded just like yours with the bright cap off.

Is this an otherwise stock 1987 ?? Seems a little dull even with the cap in, so wonder if there are other tweaks that bring it closer to Bass spec.
When I had a stock 70 Superbass I used to keep the Bass on zero, Treble on 10 and Pres on 7 and that gave me a tone that was closer to your bright cap on tone.
And when I put my stock 71 1987 at anything above 7 the Bass has to be set very low and the Treble quite high. The Treble control is way more influential for high end than the Presence IME so you would have been better off keeping that on 10 and the Presence on 5.
I guess what I’m trying to say is you have to treat the EQ very different depending on wether you’re running cap in vs cap out, wether the amp is Bass or Lead spec, and most importantly where the Volume is set.
Just leaving them either full up or half way doesn’t give you the best sound.

Also, before you start playing it shows the inputs jumped with Vol2 quite high. Is that what you used for the playing demo ?? If you want a true demo of the effect of the brightcap you should have ditched the patch cable and put Vol2 on zero. No wonder it sounded dull even with the cap in. Bass on 10 and mixing in heaps of channel 2 is a recipe for killing the classic Marshall Kerrang.