That was my very same impression... I assumed the Xbox one x would provide a better hash rate too.  I’m not qualified to provide any explanation I was just repeating what @therealcrypt posted in the discord channel earlier this month.

I’m not the dev, just a random end user eagerly awaiting the ability to mine on Xbox.  You could try asking in the discord channel, there is #dev-xbone but read only to plebs like me.  But #general has all the info I posted above if you use the discord search.

Sorry I didn’t have a better answer for you...