Wow this is something demanding release for desk... I think I started an account there in a bad time.
Still just out of curiosity from who do you get such property release? I mean the building in the city? The city president...?
As for the ID it's really strange. I thought just as you've said - it's only for payments. I thought that because they let me submit photos already. BUT just yesterday I got a mail from them saying that they rejected all my photos (which they in fact didn't do) because of the missing ID.
I have mixed feeling about this website - they doesn't state which court jurisdiction is theirs (if it goes to suing them or they will sue you) what I believe is a must for any international company. Their HQ seems to be in Hongkong (or similar) but the servers in Singapore and their company registered even somewhere else (I don't remember correctly now, I was tracerounting them after some problems with ftp).
So it's all kind of spooky here...

Hi seawhisper,
The main purpose of a Property release is to prove that you've been given consent from the owner to photograph and publicize the property. This process it to protect both parties [123RF & contributor] from lawsuits. You may get your property release from the Management of the building itself.
The property release is required to be attached onto each image that consist the following:
a) Interior of a building
b) Exterior of a building (for a photo of that building alone)
If the image is of a cityscape, then a release is not required. (the Fair Use Rule applies).
For the email that you received, we've rectified the issue and your ID has been approved.
Thanks for your patience and understanding.
Cheers,
Anglee