nedarim 52a - bitul

the ran has a basic approach that the more difference the issur is from the heter, the morelikely it is for bitul to take place. on a d'oraysa level the chachamim and r' yehuda argue regarding min b'mino. r' yehuda holds that they are too similar for the issur to be batul. chachamim hold that we focus on the difference in the issur aspect, not the type of food, and as long as the issur and heter are from the perspective of issur, bitul can take place. therefore davar sheyesh lo matirin which is slightly similar to the heter since it will be mutar, there is only bitul b'sheino mino but not in mino because mino is too similar to the issur (but eino mino is different in the type of food which compesates for the similarity of davar sheyesh lo matirin). however something hich is mutar now just that it is fleishig cannot be batul even in eino mino to allow eating with dairy, since it is even mutar now it is too similar to the issur to use bitul. is this a chumra d'rabonon like davr sheyesh lo matirin, or is their no bitul even m'doraysa?