Honest question, do you think a 2x factor of error is all that significant? Maybe it's just my EE background (where everything is measured in logs) but anything within an order of magnitude seems accurate enough for me.
Are you being serious? Saying you have 100k users when you actually have 50k is not fine, no matter your background. Hell, is it fine if I take an appliance that works on 110V and plug it into a 220V outlet? I'm also an electrical engineer and measuring everything in log scales doesn't excuse lying.
It's not about how significant the error, but that they don't care about their quality. When they interview someone without verifying that person actually works for a company, it shows they don't care about their quality.
They could fix it afterwards, but they don't even do that.