Oh yeah, you're right, wonder how he did that. He must have swept all of them somehow... don't understand how since its not a real bitcoin address.
its an old style multisig address thats how
m-0fd46773b2543ccb2ae663ff13fdfb71 translates to 4E6wXFuMixFc8LU8n5eUUG1FPY71BHZRfy
or splits to:
12niGJ1B66V668fTmgNF1gLhvH94VfabW1
18MXco4a3y8eLFcpsqV6ASpqjUxeVVEGg1
1HbJtt8hm7TGd2DhHvxuw4BRdZsd2iuxYp
you just then need to sign by using the keys (EG a 1-of-3 using the key of 1hbJtt8hm address)
and yes all the 173 multisigs have the 1hbJtt8hm in them so its easy to sign a multisig
and if you take the tx back by one taint. you will see the creator funded those multisigs using the 1hbJtt8hm address using normal legacy spend of that address so he has control of the key for the 1hbJtt8hm address to then use as a signer for the multisigs that have the address as part of the combined multisig