The pepper X thing has a long history of dissapointments, read some of these.
https://buypepperxseeds.tumblr.com/
https://www.heraldonline.com/news/lo...178278561.html
Go down to post 51.
http://thehotpepper.com/topic/66905-...missing/page-3
As far as mustard colored peppers it's hard to say exactly what you have because of the many crosses scattered around then picked up by seed companies.
This is from post 26 of the above thread.
My friend Chad crossed a chocolate bhut and a douglah. steven grew some of the seeds out and then crossed it with a trinidad scorpion he says. There are several variations of the bhutlah that i have from chad, jack and steven. Bhutlah Cheesehead is one. Bhutlah SM another. Bhutlah CS Bhutlah JC they are abbreviations for peoples names. Not that complicated to figure out. Ed Currie was given seeds and grew it out for a few years in large numbers before seeds were sold. You also have Bhutlah PL and this dave minor guy claims to have his own version too. That pepper got hyped up and blown out before anyone got to grow it really.