I wouldn't say they compromised launchpad so much as, in typical Big Chief style, they never gave us all of the relevant information to begin with. I am fully willing to believe that, internally, 350 was always the minimum launch target, and that they just hoped to pre-sell the entire run, and let people believe or assume that was the target without saying otherwise (despite being asked, repeatedly). They may well believe not sharing that information until the end would get them more sales overall, but personally I believe the opposite is true, and for many people seeing such an unlikely high assumed target would have a discouraging effect on sales instead.
Either way, I do feel not communicating this kind of information at the start clearly and cleanly does hurt them and risks further eroding confidence among customers over the long term, though. Partly because while supporters will still be glad to see it go ahead, it does risk feeling a bit bait and switch, and partly because if you don't give people all the relevant information they feel they need up front, then people will make their own narratives and leap to their own conclusions to fill in that information gap for themselves. And not just for this release, but for future releases, too. So now they potentially risk being hoist by their own petard, and if, for example, the next Who release with a 500 run doesn't launch at 350 as well, but failed at the same sort of number, regardless of the reason why, I could see a pretty sizable backlash coming their way, particularly from the core, rusted on customers.
Much like not explaining and making blatantly clear the ex-VAT pricing thing in big bold letters, so every potential international customer who may be new to all this understands what the pricing means and actually is to them (particularly when new customers are the most valuable customers to lure in), and just like not putting photos of the second painted head sculpt prominently on the sales page when it was ready, BCS (still) not putting the true launch target, as well as the 'sold out' run target, up on the page completely mystifies me to be honest.
Sad thing is, if they had been clear about the true target up front, the story of this launch would have been a far more positive "wow, look, we sold the 350 we needed and nailed the launch!", instead of the story being "damn, we didn't get close to 500, and now we're struggling just to hit 350", which is where we are at now, in my opinion. Pre-selling 350 units and getting this into production should feel like a triumph, because it is actually a hell of an accomplishment, but doing it the way they have done makes the achievement feel more like a consolation prize, and like the line is being propped up, rather than it having proved to have the support it needs to continue on. But BCS will BCS, I guess.