I can see an advantage in having all the pergolas maintained the same way at the same time by the OC, but the cost should then be levied back to the 75% of owners who have them.
I think the 75% taking a decision that clearly benefitted themselves to the detriment of the 25% could be challenged as an ‘oppression of the minority’:
https://en.wikipedia.org/wiki/Shareholder_oppression
We have carports that are used by the majority but not all owners and something like a NSW bylaw in effect that has the OC arrange for maintenance when required (eg. repainting them all) but the costs are then recouped from those owners that use those carports.