The information I provided was taken directly from a contact at Samsung. I'm currently testing KNOX functionality for another company and ended up running into this issue during some routine remediation testing. I now have a i9505 that is useless to test KNOX with.
The process I followed was this...
1) Start with MH1
2) Use CF-Auto-Root tool to root device
3) Use Odin to re-flash MH1
Samsung has said that they have had a handful of reports (4 or 5 total) that re-flashing MH1on a device with MH1 switched KNOX Warranty Void flag to 0x1 and advised us against doing this.
The only information I was given was what I posted. I don't feel comfortable answering your question since Samsung stated to me that the KNOX Warranty Void flag can not be changed back once changed.