If true, that would be evidence that meditation changes one, and might be evidence that meditation deserves further inquiry, but since suppressing one's startle reflex does not in itself have significant positive effects on a human life, it says nothing about whether the changes considered as a whole are positive or negative.

My impression at age 50 is that the 'fuzzy' self-improvement advice I took to heart was helpful in some ways and harmful in others with no significant net-positive benefit. By 'fuzzy' I mean that the advice might have 'made sense' in several ways and might have been supported by enthusiastic testimonials, but was not sigificantly informed by settled science. The OP's advice is clearly 'fuzzy' under this definition.

If we were to read the relevant peer-reviewed medical articles (search engine target: mindfulness-based stress reduction) we would probably find solid evidence that meditation can significantly lower stress hormones, but that you only need to do it 4 minutes a day to derive that benefit.

I believe that for people with certain chronic illnesses, specifically certain kinds of infections, meditating an hour a day would be very harmful because it would supress the immune system for a number of hours after the meditation session. Note that quite ordinary things that healthy people can just shrug off, such as half an hour of sun when the sun is high in the sky, suppresses the immune system for a number of hours and consequently can be very harmful to sick people. Note also that controlling the effects of (my own) chronic illness has been my number-one concern for most of the last 25 years.

In contrast, I expect no adverse health effect even in very sick people (e.g., AIDS patients) from the four-minutes-a-day regime as recommended in mindfulness-based stress reduction, and to distinguish that from what the OP is talking about, I will refer to what the OP is talking about as 'intensive meditation'.

I would also note that enough English-speaking people have tried an intensive course of meditation such as that described by the OP that even if intensive meditation had zero effect on a person, I would have expected (based on just 'raw numbers') to hear of at least one meditator who is notorious for inventing a new kind of machine, discovering a new scientific law or for some other improvement to our civilization, but I cannot recall ever having heard of one. (I would love for someone to correct that deficiency.)

In comparision, Steve Jobs and Kary Mullis (inventor of (the first really important kind of) PCR) have taken LSD, and Steve claims that it was one of his 3 most important formative experiences, and there are probably at least as many English speakers who've tried intensive meditation as have tried LSD. I could also name a number of similarly seminal, fertile or creative people who have learned to play and to love playing a musical instrument, to give another example that stand in contrast to the situation with intensive meditation.

In other words, I have a habit of noting the biographical details of people I consider to have made a significant contribution to our civilization, and I am beginning to suspect that there is something about intensive meditation that makes one less likely to make a significant contribution to our civilization. I realize of course that there are other ways of leading a worthwhile life than becoming notorious for a significant contribution to our civilization, but well a lot of us here are interested in that sort of thing (which is often called 'saving the world' around here).