Updates with answer at bottom
Today, 4/15/2019, I went to my scheduled biometrics appointment where I received the same slip of paper shown in a previous question: Why are UK visa biometrics appointments suspended at USCIS Application Support Centers?
One answer to that question quoted from the VFS Global website:
If you are an affected customer and have missed your appointment due to this service interruption, you may present at your chosen ASC location on a ‘walk-in’ basis, as soon as you see the message on this page that service has been restored.
However, the VFS Global website currently doesn't mention this bit about a 'walk-in' basis once the problem clears up. Does anyone have a screenshot of this earlier update? My stage 1 visa endorsement letter is only good for three months, two and a half months have already passed, and my worry is that even if this issue does clear up before my letter expires, I'll have to reschedule a biometrics appointment and with the backlog of applicants, the earliest possible appointment time may be well after my letter expires. My hope is that with this evidence, I may indeed walk-in at my appointed ASC location even if VFS Global later decides to do reschedulings rather than take walk-ins. I realize it's quite a long-shot.
Also, any update on the why these services have been suspended?
Update on the why: Bureaucratic glitch: UK suspends visa enrolment for American citizens
Update on Walk-ins: According to the most recent update on the VFS site (VFS UKVI Update) biometric services at non-premium ASC sites will resume April 18th. They are assigning dates on which you may walk-in at either PACs or your original ASC based on your original appointment date. Reference the table below.
Update 4/18: Despite my original appointment being on April 15th and therefore I should wait to go on April 25th, I took my chances and just walked in this morning. Nobody hassled me about showing up on the wrong date. My application is now in the hands of UPS and VFS.