I understand what you say and my reasoning was the same as yours. But I tell you that I clearly saw voltage spikes with a setup like this, but only after 30 minutes to an hour of the alternator running without a load besides the Orion chargers (bow thruster not in use).
What I think is the explanation still stands as discussed here. A voltage drop of even 0.1V is sufficient to momentarily disconnect the battery from the alternator when the battery is fully charged, regardless of the voltage lock setting.
However, your setup has 2 separate batteries, including the engine battery, while mine has only 1 (bow thruster battery), so it may be why you don’t see the issue.
Anyways, if you decide to keep it, make sure to check the voltage regularly over a long period (several hours) to make sure that there is no spike. If you do see a problem, make sure to post it on this forum so other users are aware. Hopefully my issue was for a different reason that doesn’t apply to your setup.