You may be SLF, but you have made a very salient point, that the pilot knows the trim state because he put it there.
Earlier designs (thinking DC9/737) kept pilots in the loop whilst auto-trimming, by either having an irritating honking horn, or a chunky great blo@dy wheel clanking round. In this accident of course neither would have auto-trimmed, although the Turkish accident in AMS showed us another danger of auto-trimming, even on a dinosaur like a 737.