733 Gear not locked down QRH query

[Centaurus]

It is also why you spend so much time in ground school learning the systems.

Well, yes and no. The CBT gives you bare bones information in theory enough to get you through the type rating. Need to know as against nice to know.
The FCOM goes into the systems a little deeper. The real systems experts were the old school chalk and talk engineers who took you through each system in great detail in the classroom.

Whether you actually needed that detailed stuff to safely fly the aeroplane is debatable. But certainly that detailed knowledge could be handy if of course you ever remembered it in the heat of a complicated non-normal. Hence the beauty of the QRH. In the majority of non-normal situations the QRH is the safest way to go and also keeps the lawyers at bay.

[frontlefthamster]

...or hence the ugliness of the Airbus ECAM philosophy and function, in event of what it sees as multiple failures, which aren't, generally concerned with nasty electrical happenings.

Regarding the 737 gear, I have twice persuaded recalcitrant gear to behave by re-cycling the system. I think I recall that re-cycling is advised against on the grounds of the time it takes, not for any good engineering reason. Considering the likely failures that would lead to gear not locking down, I'm not persuaded that any of them could propagate from one gear to another.