UK parliament is sovereign?

Clause 38 in the EU Withdrawal Agreement Bill has received no mention by MPs, MSPs, the media or even social media. Yet its consequences could be very far reaching.
Clause 38 in the Bill asserts that the UK parliament is sovereign. This is, according to Carwyn Jones, Former First Minister of Wales, a convention, with nothing in UK law to confirm it. Jones, a former barrister, was speaking at the Welsh Constitutional and Legislative Affairs Committee on 13th January 2020.
Prior to the 1707 Union, the English Parliament was said to be sovereign, but this was never the case with the Scottish Parliament. Sovereignty in Scotland lies with the people. The UK government is set to override Scottish constitutional law.
Listen to what Carwyn Jones has to say, about one hour twenty one minutes in, here.