ULondon & Coursera

[smartdegree]

But aside from the main colleges, the others don't. For those doing online (or in person) study with the University of London, the diploma also names the member institution of the University of London which provided the academic direction. Someone who attended Queen Mary would receive the same diploma as someone who attended a UoL program online with academic direction from Queen Mary, just as an example.

I'm not sure where you get that information.  QMUL says in its own website that it has been awarding its own degree since 2014. 
Here's what the current Queen Mary diploma looks like:
https://imgur.com/a/mv2FMES

I have no argument with you because I agree that the University of London USED TO exist like you mentioned.  Today, the old version of the University really doesn't exist except as a club sharing certain facilities in the London area.  

Also, UCL was granted degree awarding powers 17 years ago.  I apologize for rounding this off to 20 years - my bad.

According to wikipedia (sorry for the lazy reference), 10 out of 17 members of the university exercise their right to grant their own degrees.

(WIKIPEDIA)
Member institutions of the University of London
For most practical purposes, ranging from admission of students to negotiating funding from the government, the 17 member institutions are treated as individual universities. Legally speaking they are known as Recognised Bodies, with the authority to examine students and award them degrees of the university. Some member institutions also have the power to award their own degrees instead of those of the university; those which exercise that power include:

City, University of London
Goldsmiths, University of London
King's College London
London Business School
London School of Economics and Political Science
Queen Mary University of London
Royal Holloway, University of London
SOAS, University of London
St George's, University of London
University College London

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This is what a current Goldsmiths degree looks like:
https://imgur.com/a/zsXmYYD
https://imgur.com/a/dSfBbzS

Goldsmiths currently awards its own degrees and it no longer awards University of London degrees.