STM32WB55xx reference manual, section 3.7.2 specifies startup on MCU - first 1.8V and then 3.6V for USB, (Vusb must be started when Vdd is at least 1V). If I fail to follow it, what happens ?

[MReiv.1]

Its easy to fulfill requirements for startup ( I turn 3.6V LDO enable with 1.8V voltage), but when powerdown, the 3.6V decay is much longer and if 1.8V is already decayed, there is still 2V on 3.6V power line. Will this physically damage MCU or will it mess with brownout detectors ? Help ! :)