In that clip it looked to me like he was using his Sharingan to rewind time, which is different than what Izanagi does.
But even if he was, I'm not sure those clips are canon.
Stealing other people's Kekkei Genkai probably happens more often than you think. After all, there's entire corps of ninja dedicated to making sure bodies don't fall into enemy hands.
The 1st Hokage is probably not the first Senju to have his body fall into Uchiha hands.