As kim demonstrates, even 'look and say' learners should be able to pass the test. In fact, the RWI training demonstrates how adults use phonic knowledge to decode new words- but at a syllable level rather than grapheme level, and using previously learned words to extract the phonic knowledge. They gave the example of 'eudaimonia' which is a real word that many people haven't heard of, but nevertheless most people could pronounce correctly. Most adults would read it as 'eu' as in 'euphemism' (you) 'dai' as in the welsh name (dye) or as in daily (day) 'monia' as in 'pneumonia'.
So bearing in mind the phonic test for year 1 children contains real words which conform to regular phonic rules, and non words which have been formed by changing one letter of a phonemically regular word, adults should be able to read them by analogy to the original word iykwim. So if they change 'bus' to 'vus' the adult would register that it looks like 'bus' and should sound similar.
And for graphemes that are regularly pronounced in 2 or more ways, either of the regular pronunciations is acceptable. So 'bown' pronounced to rhyme with 'grown' or with 'brown', either would be correct. What wouldn't is the mistake many below average children make- which is to 'sound out' each individual letter b o w n and come up with something like bowwun.
I would find it hard to believe that any NT native English speaking adult, (given the same conditions as the children with the aliens indicating non words, and one word per page in a clear font and no time limit) could fail the test. Make one or two errors maybe as a result of carelessness, but you usually need to make more than that to fail.