This past shabbos the Rav in shul asked this question of why we say Lag Beomer and not Lag Leomer (according to minhag sfard) ???
He answered that Belz doesnt say Leshaim Yichud on 32 of the Omer bc the Nodah BeYehuda was anti Leshaim Yichud, so on his Yurtzeit they omit it. The Mechaber in shulchan orach writes LeOmer but the Rama writes BeOmer. Guess whose Yurtzeit is on Lag Beomer….???? That’s right, the Rama’s yurtzeit. So that is why we say Lag Beomer, out of respect for the Rama.