Is PIM really required to route multicast between VLANs on the same switch?

We have multicast senders on one VLAN and clients on another VLAN. Multicast routing is enabled on the switch and IGMP querier is configured on the client VLAN. My engineers are saying that the switch will not route the traffic unless they also enable PIM on both VLANs. I always though PIM was only needed if there were multiple router hops in a network. They say they are seeing this on both Ruckus ICX and Cisco Catalyst switches.