Question

Have a good week, Rabbi,
In tractate Berakhot 21a it says:
Rabbi Yohanan said: We learn the blessing over Torah after it from Grace after Meals by a kal va-chomer, and Grace before Meals from the blessing over Torah by a kal va-chomer. The blessing over Torah after it from Grace after Meals by a kal va-chomer: if food, which does not require a blessing before it, requires a blessing after it, then Torah, which requires a blessing before it, all the more so should require a blessing after it. And Grace before Meals from the blessing over Torah by a kal va-chomer: if Torah, which does not require a blessing after it, requires a blessing before it, then food, which requires a blessing after it, all the more so should require a blessing before it. But this can be refuted: what is unique about food is that one derives benefit from it; and what is unique about Torah is that it is eternal life! Furthermore, we learned in the Mishnah: for food one blesses after it and does not bless before it! Refutation.
I wanted to ask: how does Rabbi Yohanan derive two kal va-chomer arguments in opposite directions? After all, if one is more stringent than the other, then necessarily the second is not more stringent than the first.
With blessings,‎