The -new-tab switch really should have a seperate entry
in the man page to help draw attention to it's existence.
Both -new-tab and -new-window switches should be listed
as part of the output for -help, to make people aware
of their existence, so they can use them.
(I seem to recall at one time they were part of -h output, but
I may be wrong about that.)
These have accessability/usability implications
for people who may want to minimize use of the
GUI (for example due to preferences of screen reader technology
for the visually impaired.), increasing interoperability
with other software.
As a use case someone passing a URL from a text mode browser
to Firefox when Iceweasels javascript or multimedia capabilities
might be desired for special web pages, but other factors
give a preference to the text mode browser as much as possible.