I think the A14 is layered over LPDDR4X, not LPDDR4 as this article currently indicates. Your previous teardown of the iPhone 11 Pro shows the A13 over LPDDR4X and the teardown of the iPhone XS shows the A12 over LPDDR4X. It is unlikely that Apple has reverted to LPDDR4 for the iPhone 12 Pro.
The Micron MT53D512M64D4UA chip is better described as an LPDDR4X SDRAM. According to the Micron DRAM Component Part Numbering System the MT53D prefix decodes to (MT = Micron Technology, 53 = LPDDR4, D = 1.1V Vdd / 0.6V Vddq), LPDDR4X is identical to LPDDR4, except that the I/O voltage (Vddq) is reduced to 0.6 V from 1.1 V, which appears to be the case for this chip.