The existence of the BoM is a miracle in itself, and is the root and base of all of the church’s claims to truth.
Yes, for those mormons who could care less about archeology, the mere exisitence of the BoM is sufficient proof that what it says is true.
Those that do like archeology are trying to use physical evidence to prove the BoM is indeed like the bible as you suggest, as we have originals of neither one, and they are more open to the suggestion that the history of the BoM may not be entirely accurate, and utilize exaggeration or writer’s choice like the biblical writers did in some cases.
Remember, according to the revelation of the church, JS actually found the very plates the BoM writers composed it on along with other artifacts, like swords, the Urim & Thummim, and a breastplate (no centuries of scribes copying it for him, no; these were the originals, penned/imprinted by the authors themselves). Additionally, as they were translated by the power of God (rather than by linguistic knowledge), then what they say must be true, because God cannot lie.
So, if you believe that they existed at all (in a literal sense), then it inescapeably follows that you believe what they said is also true, according to mormon logic. Only those who reject the “fact” of the literal plates, and accept it as a revelation that JS authored (rather than scribed) have sufficient room to argue that the BoM events (as it is mostly historical in nature) are allegorical, rather than factual, therefore archeological evidence is unnecessary, and the BoM is “true” in the philosophical sense rather than the historical sense.