Sechel, chas veshalom to say that the tanya says that tefilah is the ikkar and not Torah; i don’t know how they twist the sefer, but I’ve learned it, and the way he describes torah is food for the neshoma, dveikus that no other mitzva – including tefilah – brings(perek 5, and 25)(or 23, i forget))
And allowing an issur that might be deoraysoh is not “simple.”
And where do people get a heter to eat whatever they want? The shu”a harav doesn’t say to have a meal. He says you can eat IF you need to for kavanah; who decided that everyone needs to eat to have kavanah? I daven with more kavanah by shacharis than i do by mincha, after i have eaten; I’m not the only one. How can you be koveah a minhag/heter that’s universal when people are different?
As for learning about Hashem before davening; who says such preparation is allowed if it’ll make you have to violate an issur of eating? Maybe the shu”a harav allows eating in order to do the basic mitzvah of tefilah with kavanah; who says it’s mutar for tosefes?