2012R2 / Windows 7 MSTSC concurrent sessions behavior

hello,

our environment follows:

2 rds hosts, 2012r2
1 host running gateway, web access, connection broker, 2012r2

client: windows 7

the client has 2 .rdp files on desktop. saved 1 rd web got config rows in there (workspace id et cetera) , made copy, changing user name in second copy.

here's issue:
1. user connects 1 session , logs in full desktop
2. user minimizes session , connects using second .rdp-file, has user name specified
3. new mstsc windows connects rds host, instead of saved username, user reconnected first session minimized in step 2.
4. looking @ first mstsc window, there's information box letting user know disconnected server

so, in short: connecting second rdp session same collection/workspace ignores saved username in rdp file , instead reconnects first, live session.

question; expected behavior in 2012r2 rds?
trying connect 2 concurrent sessions different user accounts. there setting can modify meet goal?

if connect first session, right click , modify rdp-file, change username, , connect, 2 concurrent sessions different accounts (the goal scenario). can't figure out why exact procedure changes result.

open .rdp file notepad , add line:

disableconnectionsharing:i:1

it make separated connections

Windows Server  >  Remote Desktop Services (Terminal Services)