Subaru Forester rattling gearbox after switching to single mass flywheel

Does this sound mean immenent death of my gearbox? Did I make a mistake putting a single mass flywheel in a forester?

I recently blew out the clutch on my 2002 Subaru Forester (SG9 2.5L manual dual range version)

In order to save some coin and under the advice of my local mechanic, I put in a single mass clutch instead of a dual mass clutch.

The gearbox would make some crazy race-car sounding transmission whine when I was in low range, and rattle like crazy below 2k RPM, but I didn’t think too much of it, until this week.

I pushed it pretty hard off road last weekend, getting bogged in a bit of saltwater and deep sand and now it makes this noise:

https://www.youtube.com/watch?v=2O_s9BCPobk

My mechanic thinks I’ve broken a bearing in the gearbox and need a new one. I’m a little suspicious that we cut a corner with the single mass flywheel and that’s why it’s now broken.

Has anyone had much experience with switching to a single mass or these dual range gear systems?

The sound goes as follows:

Engine on, Stopped, clutch pedal all the way in: no sound

Engine on, Stopped, clutch pedal released: Popcorn like rattling from gearbox

Engine on, low range gears selected, stopped, clutch pedal released: Popcorn monster in gearbox

Engine on, 1st gear accelerating: Popcorn like rattling from gearbox

Engine on, low range selected, 1st gear accelerating: Loud popcorn and grinding transmission whine

Engine on, cruising in 3rd gear high range down hill: minimal popcorn noise but still noticeable if listeting closely