Downgrading from 4.4 -> 4.2.6 -> 4.2.x (x < 6) is not allowed. The current state of 4.2.6 will always write out log version 3 which earlier 4.2 versions understand. However, earlier 4.2 versions will fail to startup on the checkpointed data files in a messy way (likely a seg fault)
Instead, 4.2.6 could discover if it's reading log version 4 records at startup (which is only possible via a 4.4 downgrade) and choose to write out log version 4 records. This would result in earlier versions failing with an "incompatible log version" error.