What is bad is this state where companies expect open source to cater to their whims and not putting in the resources to help maintain/develop projects with stretched resources - that is far worse than the (dubious) unprofessionalism of the Bootstrap maintainers' decision here.

Bootstrap 3 is probably more stable than the CSS most people typically write in all probability. I don't see the problem here, and this typical knee jerk reaction to carefully made open source decisions really sucks & does a disservice.