> should the bigfat files be re-joined, or should they show as separate files
They're only "rejoined" by the BigFAT compatible filesystem driver on access. By running such a driver, you're agreeing that such files should "appear" as one.
Hey, notice that you're suggesting that BigFAT should be disabled by default here; you think the user should have to choose to be running a driver with BigFAT-support. Maybe reflect on whether that's a desirable situation, or if it would've been preferable if the feature could've been enabled by default.