Hi Frank,
Without knowing the exact configuration and design any details are a bit tricky to tell, however in general you shouldn't be worried.
With MLAG, traffic that is being sent to the host (in your case the EMC) from the network is always being sent out the local MLAG port and never over the ISC to the peer for forwarding to the host.
Let's take the topology in this link for example:
https://gtacknowledge.extremenetworks.com/articles/How_To/How-to-configure-MLAG-in-Extreme-switches
Traffic going to the server that enters the switch on the left will always go via the direct link to the server and traffic that enters this MLAG setup via the right switch, will always take the directly connected link on the right. There is no algorithm needed, as this traffic is never being load-balanced or shared between the two links. The forwarding happens always locally, so this is something that needs to be considered in the design (i.e. when blocking certain links with STP, EAPS or similar).
The only part where the sharing algorithm does play a role is on the host itself (in your case the EMC) with traffic leaving the EMC and being sent out into the network.
Here the algorithm simply decides which of the two links the traffic should be placed onto, but for the EMC it doesn't matter if the other side is now one, or in case with MLAG, two different switches.
Please be aware that this is a bit different when using a two-tiered MLAG setup, as in this case the MLAG peers will also act as host and therefore have a shared link to additional MLAG switches.
