Also I'm not quite sure I buy the argument that the birth date dialog was bugged. Defaulting it to the current date is dumb, but was it really non-functional for some users? Really? Or did some users just click past it unthinking, annoyed that they were being asked something without bothering to stop and look at what they were being asked? The later seems more likely to me. These users would doubtlessly be annoyed, but what really can be done about that scenario? Those users should take it as a learning experience and be thankful TikTok is a thoroughly frivolous platform so they lost nothing of worth this time.
I don't think the problem was defaulting to the current date. No default is probably better in general for this sort of thing, and in hindsight it definitely would have been better in this case. But for a field for which you really need the user to provide a value, if you're going to set a default, that default should be obviously and universally invalid (the current date qualifies for that when you're asking for DOB), and you should have logic in place to deal with obviously invalid inputs.
Asking for a photo ID was probably easier for them than asking for a credit car though, since with the credit card method they now have to worry about PCI compliance. Getting themselves out of one regulatory shithouse by walking into another probably wasn't something they were eager to do.
They could ask the appealing user to upload a quick video of themselves requesting the appeal, and then use common sense to grant the appeal to people who reasonably appeared to be adults. That might make the FTC upset with them a second time though, since you'd doubtlessly have kids filming and uploading appeal videos, which would probably put TikTok back in violation of COPPA...
I don't think asking for a link to other social media like facebook would help, because even though Facebook is presumably in compliance with COPPA, somebody having an account on Facebook and being in compliance with COPPA doesn't necessarily mean they are >13 years old; their parent or legal guardian could have given them permission to use facebook, but not tiktok. So you can't assume that control of a facebook account means they're >13 or have parental approval to use your service.
There might be other ways out of this mess, but I can't think of any at the moment.
What matters is the result, not some technicality like whether the form worked correctly in every browser.
And the result was bad. No users were actually zero days old but they got their videos deleted just the same.
When you get bad results, don't blame the user for not understanding your system. It's always a bad design.
See also: Boeing 737 Max
Easy--never create an input field where clicking through on the default value is guaranteed to do something the user doesn't want, irreversibly. That's terrible design.
They'd go from "wtf stop asking me questions" to "you don't need to know that about me" to "wtf I'm locked out?" in about 5 seconds flat. And I don't think there is anything you can do about that. If they implemented a second chance system ("are you sure about that? input a different year or we're going to lock your account") it sounds like that would be another violation of COPPA, defeating the point of the whole ordeal.
Sorry to break it to you, but this happened to my daughter. Defaulted to 2018, she saved quickly (assuming her birth year was the default) without noticing.