Non-parsed elements becoming (partially) parsed hurts existing downstream users?

[EricCousineau-TRI]

Example issue pointed out here, which broke our functionality (upgrade from 9.1.x to 9.2.x):
RobotLocomotion/drake#13201 (comment)
In Drake, we were manually parsing //collision/surface/friction.

However, due to:
https://github.com/osrf/sdformat/blame/c6dac91c7845b0c45611e4db338e240bd86049d8/Changelog.md#L45-L46
https://github.com/osrf/sdformat/compare/a3468560e199a2723bf6ef544d338af82eea6871..76d1e4dc3257c6a529fa77b741b7fcdb67e0b1b6

For whatever reason, this same code path no longer works.
I currently cannot say why this has happened, as the raw XML should still be there (at least per the spec)?

I believe this is a bug, and should be fixed.

\cc @azeey @scpeters

[scpeters]

I commented on the drake issue RobotLocomotion/drake#13201 (comment)

[scpeters]

I've submitted a reversal of the recent behavior change in #268, but I think the drake code is brittle and should be improved.

[scpeters]

I think the behavior change was fixed by #268 and upstream drake code is being updated as well