What really matters is that there's a coherent policy for assigning addresses, which is absolutely compatible with having multiple DHCP servers on the same subnet (e.g. each server configured to hand out non-overlapping IP ranges).
It's less about the IP ranges they're giving out not overlapping and more about the requests that they respond to not overlapping (or at least that they don't contradict one another). The classic 'someone plugged a consumer wifi router into the office/university network' problem often is made worse because the consumer wifi router gives out different addresses.
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What really matters is that there's a coherent policy for assigning addresses, which is absolutely compatible with having multiple DHCP servers on the same subnet (e.g. each server configured to hand out non-overlapping IP ranges).
It's less about the IP ranges they're giving out not overlapping and more about the requests that they respond to not overlapping (or at least that they don't contradict one another). The classic 'someone plugged a consumer wifi router into the office/university network' problem often is made worse because the consumer wifi router gives out different addresses.