Hampden chiefs want to have plans in place in case season ends early.
The Scottish Championship will be the only senior division to continue to allow a maximum of three substitues during the 2020/21 season.
Only three of the ten second-tier clubs voted to allow teams up to five changes during matches.
The lower league seasons begin on October 17.
Leagues One and Two have approved the switch to five subs for their new campaigns. Only one club across the third and fourth tiers voted against the change, which has been in place for the Premiership since it began in early August.
Meanwhile, five subs will also be allowed in Betfred Cup and Challenge Cup games, with on additional switch allowed in extra time.
The end of season league play-off matches will, however, revert back to three changes, with one more sub allowed in extra time.
“In line with last season, FIFA has allowed each league to determine its own rules regarding the use of substitutes for Season 2020/21, due to Covid-19. As a members’ organisation, it is important that the clubs in each Division decide issues such as this for themselves,” an SPFL spokesman said.
