Ramban disagrees and brings many proofs that the second shem, the Y-K-V-K, refers to Hashem’s attribute of mercy.
Maybe the machlokes here is whether the shem should be interpreted based only on how it is read, i.e. Elokim=justice, or whether it should be interpreted in light of how it is written, i.e. Y-K-V-K = mercy.
This is reminiscent of (though not exactly parallel to) the machlokes between Mechaber and GR”A in O.C. siman 5 regarding kavanah when reading shem Hashem. According to the Mechaber, when saying the shem Hashem one must have kavanah for the midah of the shem as written, not just as pronounced. Even though the shem Y-K-V-K is read as the shem of Adnus, according to the Mechaber one must also have in mind the meaning of Y-K-V-K, that G-d is eternal and is in past, present and future. According to GR”A, one need only have in mind the idea of Adnus, the name as pronounced, not the Y-K-V-K as written.
The chakira raised by both the Rav and the Brisker Rav regarding what the gemara means when it darshens that we are supposed to pronounce the shem Adnus when we see Y-K-V-K may hinge on this issue. Does the gemara mean that since we can’t read Y-K-V-K, we ba’al peh substitute the shem Adnus when we see those letters, or does the gemara means the shem Adnus is the way to read/pronounce Y-K-V-K?