Why does it need a response, you answered it yourself...
" Due to the dropout behavior of the LDO TL5209, its output voltage
rail SYS_VDD1_3P3V should not be used when the OSD335x is being
powered through VIN_BAT. Please refer to the TL5209 datasheet for
Supplying an IC that requires 3.3V or more with the output of the TL5209 is definitely not the right choice as:
3.7V (min battery voltage) - 0.06V (typical value of the battery switch dropout voltage V_DO,BAT of the PMIC (p. 9)) - 500mV (voltage dropout of the LDO @f ull load of 500mA) = 3.14V
However the 3.14V is inside the range mentioned in the datasheet for supplying the IC (2.7V to 3.6V). That’s why I am still confused.