I'm totally speculating here, but I suspect that as long as they're clearing out rates from the ads' text, they're removing phone numbers and links external websites as well. That way if they decide in the future a need to remove phone numbers, they can do it with a flip of a switch (hide that field) and not have to review every ad again. And that's the day I seriously consider pulling my ad. Else they'll mimic M4RN's (may she not rest in peace) slimy trick of leaving the ad up but with no contact info when the advertiser stops paying.
Kevin Slater