Overall Cell Throughput of single UE is lower than of 2 UEs

Hello LTE/5G Experts.

I see the overall cell Throughput of single UE (534 Mbps) is lower than of 2 UEs (553 Mbps).
What could be the reason that when I have max UEs per TTI in DL is 1 UE then Tput is 534.
But when max UEs per TTI in DL is 2 UEs then I see average Tput of the cell is 550 Mbps.

What could be the reason for that behaviour?

Maybe MU-MIMO?

Could be, let me validate. Much thanks!