No, you cannot use 2 m.2's on a B550 board.
No, you cannot use 2 m.2's on a B550 board.
He's possibly incorrect or dishonest. Typical B550 boards accommodate two M.2 SSDs. On my B450 I can even install two, using PCIe Gen3 rather than Gen4 on B550/X570. Your board can support one with a heatsink and another without. If you choose the latter, you'll lose some SATA ports. Your specifications: M.2 Port Types 2242, 2260, 2280, 22110, SATA Express, two slots, 3rd generation key.
B550 primary m.2 supports PCIe4 off the CPU, while other M.2 slots use the chipset at 3.0 X570, allowing them to operate at 4.0 with primary off the CPU and chipset off the rest.
I believe the confusion comes from older APUs. The 5600G and 5700G offer 20 CPU lanes plus an additional 4 for the chipset, matching the main 3000 and 5000 series chips. The main difference is they only support PCIe Gen 3, not Gen 4. In contrast, the 2200G and 2400G had significantly fewer lanes—only 12 total. This meant some boards faced problems where the M.2 slot connected to the chipset wouldn’t work because the CPU connection couldn’t function. Later APUs avoided this issue by providing more lanes.