I don't think "bogus self-employment" applies here. If you're a company that contracts people instead of hire them as employees you might have troubles, but not the other way around.
I can only speak for Germany and from my experience. Their argument was that you only have „one“ customer and therefor should be employed by, in this case, Paddle.
Edit: Should mention it was for a kind of SaaS, the case may be different if you sell physical products online.
Well, I guess it's quite similar where I'm from (in EU) where it depends if you're an individual or have an LLC like form of organization.
Even if you're sole proprietorship there are a things to happen to risk being classified as employee, like not setting your own working hours, working with company tools, not being able to sell to other clients (of course you can do that) and so on.
I really doubt it's an issue with Paddle, they have lots of german customers.
Edit: Should mention it was for a kind of SaaS, the case may be different if you sell physical products online.