True, we have discussed that before and the likelyhood that one and the same manufacturer - whoever it was - had several reference designs based on the TI custom chipset but with different CPUs attached to it, of which Coleco went with the Z80 design and the 6502 design was left for VTech to acquire.
Obviously the VDP and PSG originally were custom made for the TI/MB but at some point it appears to me the chips were offered to any system manufacturer, perhaps even second sourced, which is when they went from custom to on the shelf items. I'd love to find a reference to when it happened, or if it even happened simultaneously to the 99/4 release, in order to bring production volumes up and price per chip down. Then again does any system besides the TI computer use a 9918 without the A suffix to get NTSC composite video? That variant of the chip I think dates to 1981, which would be within the same year of the original CreatiVision, among possibly other designs. Or maybe a separate circuit to combine the Y, R-Y, B-Y into a composite or RF signal wasn't unthinkable, offering a market before the 9918A revision.