With the introduction of the fuses target, it looks like the fuse values need to be configured like so in your platformio.ini:
; Arduino Pro Mini Atmega328 8Mhz
board_fuses.hfuse = 0xDA
board_fuses.lfuse = 0xFF
board_fuses.efuse = 0xFD
You may not even need the extra_scripts helper any more… worth commenting that out and trying… e.g. pio run -t fuses or the Set fuses project task (I’d try it myself but don’t have willing victim or programmer handy atm).