This is an incredibly clever answer to a question that really didn't need answering, and I'm fully here for it.

Terry Nation’s misunderstanding of the word “galaxy” also explains why in Genesis of the Daleks, it’s stated that Davros says in the “Seven Galaxies” only Skaro can support life. That line bothered me even as a kid because like, how could you observe all the planets in a single galaxy, let alone seven.
If by galaxy, Terry Nation meant “planetary system”, that line makes way more sense.

A line from early Blake's 7, "Duel", written by guess who.
TRAVIS "Blake. The other patrols have pushed him into this galaxy. I knew it, I knew it! This time I've got him. "
Nothing changes.  🙂

At the end of season 2, Chris Boucher has other ideas:
CALLY "What, the space between the island galaxies. It's the nearest we'll come to infinity before we die."
JENNA "If anything goes wrong out there we won't have a prayer, because nothing and nobody goes out that far. "

I always assumed the delegates were from the Milky Way's satellite galaxies like Saggitarius and the Magellenic clouds.

Even as a kid, I was more comfortable with interstellar stories than intergalactic stories.  And it's not that I was a science wiz with a firm understanding of the distances involved, it was just that I figured if even interplanetary distances were something we had only just started to cover, then interstellar distances would give us all the storytelling space we would need for a very long time to come.

Terry Nation's misunderstanding over the term 'galaxy' apparently extended into the seventies. In the series 1 Blake's Seven episode Duel, everyone's favourite Space Commander Travis finally catches up to Blake after chasing the Liberator for some time, and remarks "The other patrols have pushed him into this galaxy. I knew it. I knew it!"

This is the best thing I have watched all year.

The dark Christmas tree alien has always intrigued me.

Quite an achievement, this video. Very much enjoyed, and appreciate the hard work, pedantry, and humour.

I'll buy it. This is allowed in my head-cannon. Well done. VERY interested to hear that even in cosmological circles these terms weren't nailed down until later. NOW make sense of The Wheel In Space's science!

You could say the Daleks constructed the Time Destructor as a way to “skirt” any interference from the Timelords on Gallifrey. If the Daleks used their Time Machine to alter the past or the future, the Timelords would be on them like a shot, but if the Daleks brought the “future” to the present, it wouldn’t technically be “interfering with time”, so much as “accelerating events”.

Hold on a minute... I'm learning stuff. Noooooo!

I can't believe that a bunch of tiny galaxies came into existence just to fix any problems with a Terry Nation script for Doctor Who. Just incredible

Before watching the video, but after seeing a couple of comments: It was quite common for TV and perhaps movie writers in the early-to-mid twentieth century to confuse 'star system,' 'galaxy,' and 'universe,' possibly due to pre-college educators in the first half of the century not really knowing the difference.

...'Cos there's bugger all down here on Earth.

You certainly earned the leather elbow patches on your tweed jacket for this excellent episode of The Open Universe(ity)

I do enjoy the references to other settings - Hitchhiker's Guide, Warhammer, and of course Father Ted.
Oh, and Dad's Army!

Getting the science wrong in SF due to the ignorance of the writer has always grated with. DMP is no exception. I've been aware of the size of space since I was a child.
Modern Doctor Who writers are no better. We in the know often assume others have at least a small amount of knowledge. When talking about astronomy I have encountered adults who don't realise the Sun is a star!

As president of Terry Nation, you continue to give us awesome examples of early who that I really appreciate.  Go Mr President go!

I didn't just sit through an almost hour explanation on how The Daleks Master Plan can make sense just to be told it isn't important 🤣

Great video guys.

You are script archeologists. Painstakingly troweling and brushing away layer by layer to better our understanding. Amazing, as ever.