VideoCardz reports MSI offered some clarification for why not all of its Radeon RX 5600 XT cards have received the upgrade to 14Gbps. The problem is that MSI did not buy the memory chips for its Radeon RX 5600 XT cards. The GDDR6 memory was supplied by AMD and was rated at 12Gbps, not 14Gbps. MSI is not the only one with this problem, ASUS has exactly the same issue. As such, the company's can't guarantee that these cards will be able to handle 14Gbps without issues.
This supplied memory was specified to work at 12 Gbps, not 14 Gbps. While it might (and in most occasions will) support 14 Gbps speed, MSI and ASUS cannot guarantee such speed. This would basically cause RMA issues for both manufacturers, who did not validate their cards to work at such frequency.
Interestingly, MSI had no problem sending 14 Gbps BIOSes to reviewers who already received GAMING X models. They were told to flash GAMING Z bios onto their X’s and rename their products in reviews. So yes, from the reviewers’ perspective, the explanation in the video is a bit embarrassing to listen to. After all, MSI did not validate their review samples to run at 14 Gbps either.