His name is Takanoyama
. He often goes for an armlock at the tachiai at the start of the bout. He has a background in judo and perhaps he was used to doing that from a cross grip. Also because he is very, very light for a sumo wrestler he has probably found that getting an angle at the start is more productive than trying to wrestle square on. Takanoyama goes for the armlock and then switches into other techniques.
The armbar throwing technique
is called tottari. It's not common but a few sumo wrestlers have had it as one of their favourite techniques.