Thinking in terms of 'ticks' over-discretises it. You can in practice measure frequency to much more precision than any discrete cycle time in the system you're

Thinking in terms of 'ticks' over-discretises it. You can in practice measure frequency to much more precision than any discrete cycle time in the system you're using, because you can usually measure phase, i.e. you're not just seeing some on-off flash, you're seeing a gradual pulse or wave, and it's how accurately you can measure that pulse (in terms of SNR) which sets your integration time for a given precision, not how rapidly you're measuring it.