From my point of view the problem is the following: If I want to quickly call, say channel 72, to check on a fellow paddler pressing the transmit button chooses a random channel from the scan set of channels. So, I have to press the channel up or down keys to get to 72. If, in the alternative, the radio is locked to channel 72 and one needs to make an immediate emergency call to the CG, the 16/C button (the emergency button to go to channel 16) doesn't work. So, one has to unlock the lock first.
The latter is the heart of my complaint about handheld VHF radios in the associated thread (Unsafe VHF Design); i.e., the 16/C button should immediately override the lock. Given enough time, someone (especially one who needs to raise the CG ASAP and is, say, using a borrowed radio) will not be able to unlock the lock and a possible preventable catastrophe might occur.