A bunch of the fighters were that way. People used to have threads about breaking them down into their kitbash parts on /m/ and here when it was airing. Now, there's exceptions like some kits made specifically for the show like Bearguy, but a whole ton of the rest were all real and from weird places. Like you'd see somebody wanted bigger boosters so they'd repurpose something off a 1/100 MG and graft it onto a 1/144. It was pretty great.
It was shown more than stated. Like think about when you watch Gundam Unicorn and you see the desert attack in Episode 4 and you can sit there and actually pick out all the different factional remnants. Like you know the guy in the Dwadge and the Desert Zakus are OYW from that village of desert dudes in ZZ. The Gallus is from the group Haman left to garrison Dakar in ZZ. All that backstory stuff just there for people who knew what was going on.
Or when you see the EWAC Zack with the Sleeves in episode 2 and remember Haman talking about folding what was left of the Titans into her forces.