Here's an overview of phones with the dual-frequency chips:
It's hard to find good info and nothing with respect to Collector. People using gps testing apps were still getting 4m at best.
The pixel 4 was just announced with this note:
⁸Dual Band (L1+L5) or (E1 +E5a). Support - coming soon
So maybe the phones right now don't have proper software support?