I know, but that doesn't mean that there aren't bugs or missing features specific to that GPU model (hardware or software). But I can't be sure whether this particular issue is a driver bug or just an unsupported combination of pixel formats (FRAMEBUFFER_INCOMPLETE hints at that).
WebGL spec requires certain of pixel formats to be supported but either the test case is using some combination that isn't guaranteed to be supported or the driver+hw combination doesn't actually support everything required by the spec.
Intel has made huge improvements since the days of the i9xx series of GPUs. They were miserably bad from a programmer's standpoint.