Not in this case and on very few obscure routes only is there "Block Space". All flights with UA/LH/BD/SK are "Free Sell". Either airline can sell as much or as little as they are able. Block space is more likely with airlines outside Star. The only one that comes to mind is Jordanian and that might have expired.

Fares coming out of whack like this is quite common for a number of reasons and maybe because of two or three at the same time on a particular city pair. The best answer is go for the cheaper fare and enjoy.