This is very common practice with most strata management companies who charge low Schedule A (Standard Fees) and encourage their managers to bill for every small item of work carried out on top.
I have suggested this on numerous posts but: choose a manager who has one up front fee or at the very least will cap the Sch B’s & disbursements.
Having said that, the traditional reason for SM’s charging hourly rates is for attendance at after hours meetings or tribunals etc. Any additional work carried out that is not covered by your standard fees will take time out of your SM’s already busy schedule. Is it not reasonable that they get paid a % of Sch B’s then to cover their overtime (esp. late night meetings)?