Note that while it is just replacing the eMMC, they are not replacing it with the exact same component. The replacement is actually a significantly larger memory chip which is expected to provide significantly better longevity than the prior eMMC chip.
Upgrade to MCU2 is much more extensive than just replacing the chip, but involves need to replace both the main screen as well as the instrument panel screen. Reason for replacing the IP screen is that with MCU2 the IP is actually run off the same processor as main screen so they must go together. Screen cost is a big part of why MCU2 upgrade is significantly more.