This way, at least you can unlock the phone with your fingerprint and still have some peace of mind, perhaps until you install a viable third-party tempered glass or polyurethane protector. Samsung has told Engadget there will be compatible third-party protectors available when it releases the phones. Samsung will also offer its screen protector separately for $30.
The issue does not affect the Galaxy S10e, which uses a capacitive scanner. The higher-end models have an ultrasonic scanner, which is more secure. But some screen protectors may block the soundwaves that scanner uses to read the ridge depth of your fingerprint, making it unusable. The upcoming Galaxy S10 5G also has an ultrasonic scanner, but Samsung didn't say whether that will ship with a pre-installed screen protector.
Update 28/2/2019 5:15 PM ET: Samsung has updated its announcement to state the pre-installed screen protector will not have a warranty. We've updated the post accordingly.