Hmph, interesting.

Google Cloud AS396982 seems to flag their customers BYOIP routes as EGP originated, something that is quite rare on the modern internet.

Example, a BYOIP JISC prefix:

# birdc s ro all 188.92.136.0/24 |& egrep 'origin|unicast'
188.92.136.0/24      unicast [transit4_1 2023-10-18] * (100) [AS396982e]
	BGP.origin: EGP
                     unicast [transit4_2 2023-11-07] (100) [AS396982e]
	BGP.origin: EGP

However a google owned prefix on the same ASN, learned by the same paths

# birdc s ro all 23.236.49.0/24 |& egrep 'origin|unicast'
23.236.49.0/24       unicast [transit4_1 2023-10-18] * (100) [AS396982i]
	BGP.origin: IGP
                     unicast [transit4_2 2023-11-07] (100) [AS396982i]
	BGP.origin: IGP

mmm, are they being sneaky with that attribute?