On the other hand, did the USS Valkyrie ever make it to the TV or movie series? If not, does this even count?
The
Valkyrie is not a distinct model, but a relabeling of the one and only photographic piece. Supposedly, the new labels did appear in some episode or another (because somebody went to the trouble of doing the relabeling, and it was not an idle labor of love because the workmanship is pretty crappy

). But neither the new labels nor the underside can be discerned in any episode or movie. And that "Peak Performance" shot, unlikely to be any sharper in the blu-ray release, is our only canonical glimpse to the bottom of the ship. Canonically,
Constellation class ships don't have undersides!
I'm thinking with those painted white in the front and lacking in torpedo launcher details that those are not torpedo launchers at all for the top and bottom parts.
The principal problem with that is that the ship does have torpedo tubes. If we give torpedo tube identity to some other fixture that looks completely unlike a torpedo tube, then what right do we have to declare that these familiar-looking fixtures are not allowed to be torpedo tubes?
It might be that the Battle of Maxia resulted in the
Stargazer having her torpedo launchers so badly damaged that we no longer can see their muzzles, and Picard would just have blown himself up when attempting firing.
For myself, I don't understand why Captain Picard ordered his ship to be abandoned.
Because there was no point in remaining aboard?
The ship no longer moved on her own. She could not take the heroes home. Shuttles could.
On the other hand, the ship no longer did anything else on her own, either. She could not continue her mission. Nobody could.
Now postulate that the ship could not be repaired on the spot, not with the resources at hand.
So, going to the shuttles and flying home would be the sensible thing to do!
Should the ship have been recovered later?
...Why bother if she was outdated junk anyway? Starfleet can afford to lose old ships; it scuttled the
Lantree instead of trying to decontaminate her, say.
Should the ship have been scuttled on the spot?
...Why? She wasn't a traffic hazard. Her falling in enemy hands should not be a problem - if the enemy wants the piece of junk, he's quite welcome, as long as Picard has remembered to push the button that erases Starfleet secrets from the computers. And perhaps some friendly party in need will stumble onto her instead? Scuttling is not particularly logical except in certain very specific circumstances, such as those applying to naval warfare here on Earth.
Timo Saloniemi