So as I understand it your RAC installation is a stretch cluster between two sites. In this case it makes sense to consider a recovery catalog in each location because the loss of one site will serious affect you if that site also contains the recovery catalog etc.
How do you maintain two recovery catalogs? There are several alternative including:
1) Backup separately in both sites.
2) Backup in one site. Transfer the backups to the second site and transfer a copy of the catalog.
Personally, I think running two separate backups of one database is a bit over the top. Especially if it gets rather big. That seems like an unnecessary overhead to me. With a RAC installation, there is only one database, so why back it up multiple times?
Personally I would pick option 2 and transfer the backups over to site 2, so you have copies of the backups in both locations, then do a regular transfer of the recovery catalog over to the second site. This could be as simple as an export from site A and an import to site B. It should be easy to script.
I guess my question would be to ask the consultant what benefits (s)he sees in doing two backups compare to 1 and a transfer. It may be the network transfer is more of a consideration than the overhead of the second backup etc. I would need to know the logic of the decision process to know if I agree with them or not.