Why does Hallel at the Seder not get a Bracha, according to the second opinion cited by the Tur?

Question

The Tur (OC 473) cites two approaches regarding making a blessing on Hallel at the Seder:

בענין ברכת ההלל איכא פלוגתא דרבוותא ריצב"א היה מברך עליו ב"פ אחת קודם אכילה ואחת אחר אכילה וכן היה נוהג ה"ר מאיר מרוטנבורק וכ"כ רב האי ורב צמח ורב עמרם אבל הרי"ץ גיאת ואבי העזרי כתבו שאין לברך עליו כלל לפי שחולקים אותו לשנים לפני הסעודה ולאחריה וא"כ האיך יברכו כיון שפוסקים באמצע וכן היה נוהג א"א הרא"ש ז"ל וכן ראוי לעשות בכל דבר שיש ספק בברכתו שאין לברך דברכות אינן מעכבות

Regarding the blessing on Hallel, there is a dispute amongst the Rabbis. Ritzv"a would make a bracha on it twice: once before eating and once after eating. Thus did the Mahara"m practice as well, and so do Rav Hai, Rav Tzemach, and Rav Amram write. But the Ri"tz Gi'as and Avi HaEzri write not to make a blessing at all, since we split it into two: before the meal and after. If so, how can we make a bracha, since it is split in the middle? Thus did my father, the Ro"sh, may his memory be for a blessing, practice. Thus is fitting to do for anything for which there is a doubt regarding the bracha, that he should not make the bracha, for brachos do not prevent.

I'm struggling to understand the latter opinion. What's the problem with making a bracha before each half, as the former opinion practiced?

Answer 1

According to my Oz V’hadar extended Mesivta Haggadah, page 725, Tosfos (Berachos 14a DH “yamim”), among other Rishonim, write that the meal is considered an interruption of the Mitzvah. In this vein, the Ra’avya (§525) writes that one shouldn’t make two Berachos on two halves of a Mitzvah.

This seems to be the rationale for the opinion cited by the Tur. Seemingly the former opinion held that granted that the meal is an interruption, there’s no problem with making two separate Berachos. Indeed, on page 724, they quote other opinions in Tosfos (ibid.) who held that during Maggid one makes the Bracha of “on reading the Hallel,” and after bentching one makes the Beracha of “on completing the Hallel.”

(I should note that many other reasons are given in support of not making any Berachos on Hallel at the Seder, but none of them fit with the opinion cited by the Tur.)