The batter should be thick like muffin batter and it is usually necessary to spread them a bit with the back of the sppon. That's the trick for getting super fluffy vegan pancakes. It should be thicker than pancake batter made with eggs otherwise it won't dry out and get fluffy. They do also take longer to cook than non-vegan pancakes. Low and slow gives the very best results.
Having said that if you didn't weigh the flour and used cups to measure instead then the amount of flour you used could have been a bit too much and made it a little thicker. Cups aren't the most accurate way to measure and you could have inadvertently used too much. A digital scale is the best way to get exactly the right amount.
The mention of water in the post was a mistake. Sorry about that. I've just corrected it. For future reference always go with what it says in the recipe card because that part is what is tested by me and my recipe testers before the recipe is published. That means it will always be accurate.
Hope that helps!

I didn't end up adding any water and the pancakes were super thick (I had to spread it out in the pan with a spoon) and it took forever to cook through because of how thick/dense it was.

All that said, the flavor was good and I'd make this again but would add more liquid as the batter was just too thick without it.

I have never tried them with gluten-free flour. Oat flour would probably work but you would need to adjust the liquid slightly as it's not as absorbent as spelt. Just add enough to make it a really thick batter, almost like cake batter and it should be fine.

That's so good to hear. Thank you!