You are correct, although I think the term isolator doesn't fully describe them. They're both solenoids, one of which is automatic and will automatically kick in to charge your house battery while your engine is running. The second, is manually actuated via a switch on the dashboard in order to use your house batteries to supply additional power (boost) to your chassis battery.
This write-up, although not Winnebago-specific, might help:
In my case, in addition to the above, I also installed an Amp-L-Start, which is the big brother of the Trik-L-Start mentioned in the article. This allows my house battery charge system (both solar and converter/charger) to keep my chassis battery charged. It isn't a solenoid but uses electronic circuitry to manage the current flow to the chassis battery. It's a fairly straight-forward installation and is a good mod to consider.