There are some valid reasons for tests like this to exist. To quote later on in the linked Tweet thread [1]:

  BTW it's easy to say this is wasteful, and it probably is, but just like with the pregnancy test, you should consider that there's three main problems that can affect the accuracy of lateral flow tests like this:
  1. inconsistent lighting
  2. incorrect timing
  3. human error
  
  having a 2$ computer chip and 50 cents worth of plastic  & lenses removes all those sources of error. 
  And making it bluetooth removes a source of e-waste! it means it doesn't need to have a screen, it can just talk to your phone.
  
  for example, consider that a bit more than 1 in 12 people have some kind of colorblindness.
  Having a computer say "POSITIVE" or "NEGATIVE" is going to be easier to see then the uncertainty of "is that stripe red? can I just not see it?"