Golly, looks like it's set up to prevent the band from sliding upward.

I guess, the aesthetic sense of the frame builder just couldn't force him or herself to install an upsidown heart on this hand brazed frame.....:rolleyes::thumb:

I'll throw a monkey wrench in here...maybe this frame with lower weird "pibb" (I call em' nubs when used for shifters) and the accompanying rare/odd clamp were designed for a Suntour reverse action/ bottom pull/bassackwards front derailleurs like the SL and early XCs (I don't know about BLs like on this bike). On these reverse action derailleurs cable tension is used to pull chain down to smaller rings, a force much greater than spring tension (standard action derailleur use the spring tension for down shifts). If this is the case, above the pibb might be correct.

Yes, it is. If I had a front derailleur installed and it used the bit of housing between derailleur and cable stop that this clamp is designed for, the housing would tend to push the clamp up. The rear cable passes through, so it doesn't pull much in either direction.