Ah! Sure enough, the new one does connect at 5 GB/s and has much better bandwidth test numbers:
% python oakbw.py
Downlink 1860.2 mbps
Uplink 1664.8 mbps
(BTW the formatting controls on this forum really suck. I can't precisely set just a portion of the text to code block style, as evidenced above by the English sentence. I'm trying to format only the python output, but it insists on doing both. I'd highly recommend changing the forum to Discourse, but at the very least maybe there's an update for whatever you use that fixes this issue? Safari 17.5 on macOS 14.5)