Re: "Solid Neutral"
Solid neutral or S/N term has been around for years & shows up on panelboard dwgs. all the time. If it helps, think of it as "standard neutral".
Yes regular equipment has a solid "neutral". It is that particular switched neutral breaker that can be installed in it for 514.11(A) applications. The picture in the Digest is of one of those breakers in which the "lead" is from the line side of one pole. That lead connects to the regular solid neutral in the panelboard. The loadside "neutral" connects to the load lug on that pole. Again, a switched neutral or SW/N is a kind of special application.
Just the fact that you can loosen a set screw & pull the grounded conductor out of its lug, or lift the lug, meets 230.75 for a service panelboard. Service switchboard or service switchgear frequently has a removable bus bar or bus link to accomplish. There are cases when testing/troubleshooting, one needs the grounded conductor isolated, & in 99.44% of the time there is not a disc. means in the grounded conductor.