A Passover question I have been asked

My Rabbi (Rav Ari Heller) sent me this amazing question. What do you think?

The question: Towards the end of Magid we read Raban Gamliel’s famous statement (which is the ikar of the Haggada and halachickly must be understood by all - if necessary, it should be translated.) “col shlo amar shlosha dvarim elu bpesach lo yatza yidey chovoto, velu hen: Pesach, Matza, Maror” He then goes on to explain each one, and teaches us that the reason we eat Matza on pesach is “al shum ahlo hispik bitzeikam shek avoteinu lhachmitz ad shnigla aleyhem Melech Malchei Hamlachim Hakadosh Baruch Hu ugialam.” (In short: In memory of what happened to BY as they were leaving Mitzrayim that they were in such a rush that their dough didn’t have time to rise.) This is a nice idea, but BEFORE that story transpired Hashem ALREADY commanded them the mitzva to eat matza (Shmot 12:8,15)???