I find the Northern route more credible with Myanmar the hole in the radar fence. They've then got very high ground to cover any intended Westward movement from the Indian radars. The altitude excursions probably indicate non pro pilots as VNAV is the more complicated mode, whist HDG SEL is adequate for LNAV using just a mobile or tablet FMC app. No need for a/c systems nav at all. I've got doubts that they made it unless the authorities in some country en-route were also in on it.