Question: Matrix, exponents and sum

I learnt that MapleFlow (MF) was a product similar (and better) than MathCad (MC). I have a old copy of MC, v.11 (with Maple symbolic engine) and I compared it with MF from my engineering dep. 

Can one kindly explain why Sum of a simple Matrix does not work, if the index is placed as exponent? Here what I did:

Please Wait...