The IRS will not know what threshold applies to a given taxpayer unless they have a reason to examine the return; if they do examine (i.e. "audit") the return and find you failed to comply with the filing threshold, they will aggressively impose the penalties that apply.
The US tax system is described as a "voluntary tax system". That doesn't mean you have a choice on whether to file a return or pay tax, it simply means that the taxpayers "voluntarily" provide the information necessary to administer the tax laws. In this case, you are "voluntarily" complying with the filing thresholds for Form 8938.
In other words, it is up to you to comply with reporting requirements and up to the IRS to penalize you if they find you aren't doing so.
