Yes actually and I wouldn't be alone. Pretty much everyone was claiming Twitter was hiding numbers during that time to cover for the fact that they had mostly inactive accounts.
Yet Twitter experienced phenomenal growth, going from zero to tens of millions of MAU in their first 4 years, proving your logic wrong (paraphrasing you, you said "if growth was so great surely a company would release MAU"). So if you apply the same criticism you make against Coinbase to Twitter, you would have said in these first 4 years "Twitter's metric are all vanity metrics" and you would have rejected Twitter's claims of growth. Well you would have been misguided, as we now know for certain Twitter WAS growing during these first 4 years.
This is why you look stupid to reject exchanges' claim of growth. Yes we know MAU is less than number_of_wallets. It's mathematical. But still, it's silly for you to reject their claims of growth as you have no basis for it. Not releasing MAU doesn't mean you are not growing, as Twitter demonstrated.
The thing is while they were refusing to release the data there were strong indications that those numbers were very weak. Seriously go read up about it.
Many people did reject Twitters claims of growth and they were largely proven right when Twitter started releasing MAU.
You call growing from zero to tens of millions of MAU in 4 years "very weak"?! Ridiculous. You are wrong, nobody seriously outright rejected Twitter was growing. The worst critics said was "Twitter is not growing as fast as they claim, but they ARE growing" or "growth has slowed down, but there are still growing".
I can use any other example to prove that not releasing MAU doesn't mean something needs to be hidden. I quoted Gmail earlier because this is a good case of a growing product whose MAU needed to be kept secret due to competitive reasons.
So what you're saying is that Twitter withheld their MAU because the figures were poor?
Why did Gmails MAU need to be kept secret?
As an aside growth at Coinbase in user accounts IS slowing quite dramatically. 350K per month for 2013, 100k per month for 2014, 50K per month for 2014.
If you knew anything about Bitcoin, you would know there are always truckloads of people signing up on exchanges whenever the price is very high. It was above $500 per coin for the first half of 2014 so this pushed user account creation to 90k/month overall for the year. Now we are back to 65k/month which has been quite constant since 2013 with the exception of the bubble craze.
This is why you look stupid to reject exchanges' claim of growth. Yes we know MAU is less than number_of_wallets. It's mathematical. But still, it's silly for you to reject their claims of growth as you have no basis for it. Not releasing MAU doesn't mean you are not growing, as Twitter demonstrated.