So I can imagine locking HBD for a time ensures some part of converted HIVE will not be dumped on the market in the given time. It makes sense from the point of value of the network. Like a HIVE freezer.

In that case locking periods should be somehow corelated with market cycles and reward should be correlated with the phase of the market. I can imagine that it'd be much more valuable for Hive to have it secured that HIVE won't be dumped during bear market. Does it make sense?