> IBM was consistent with their keyboard nomenclature across multiple products, and the 3270 series mainframe terminals used the Tab key

While it seems odd in light of IBM's usual adherence to corporate norms across business units, having read a couple different books on the origins of the PC at IBM, it may be related to the entire PC unit in Boca being an extraordinary aberration outside the norm for IBM. Despite seeming hopelessly corporate to the Microsoft team, the Boca IBMers were considered a "Rebel Unit" inside IBM - when they were considered at all, since the vast majority of IBM wasn't even aware of it.

Due to being started virtually overnight (in IBM timescales), running incredibly fast and only existing thanks to Thomas Watson, Jr. himself overruling his lieutenants to approve such a "skunk works", Boca didn't have nearly the level of oversight, coordination or control as an effort that size normally would. In the early days Boca ran largely outside normal reporting channels and when they'd try to source tech or components from other parts of IBM, had to sometimes clarify that they were in fact part of IBM.