FWIW: It turns out not to be academic in practice.
About 25-30% of the complaints about GPL violations i've seen (for example, on gpl-violations mailing lists, though at least there, there are more valid ones recently) are actually cases where the company has made a written offer, and the person's complaint is this is a GPL violation and they should have released the source instead.
Of course, this has changed over the years for the worse (in the sense that the percentage of actual compliance seems to be dropping), but it's still not uncommon.