Re: Less lead less impact.
.50 cal sniper rounds aren't for shooting hard targets, unless used in an anti-materiel role, in which case you're generally shooting at a large, static target and don't need much in the way of help.
Lighter-weight explosive 50 cal rounds have been used since WW2 and work just fine. If the mass reduction is an issue, it can be rectified by adding a tungsten pointy-bit, which weighs hell of a lot more than lead and cruises through armour quite nicey. Not that military ammunition is a lump of lead anyway.
"The course corrections looked rather abrupt on the video and not quite feasible for a ballistic object but hard to judge given no range or view point parallax info."
I'm going to bet that it was a ballistic object and that they're not lying, rather than your armchair assessment being correct.