yea, when you look at the original and the way it was supposed to work, it just doesn't really make that much sense. It somehow took your physical senses and gave you MORE input to give bonuses to combat situations... which is, a little off.
Sure, one can train their senses to get .. how shall we say.. a "heightened sense" of danger, much like police and military personal develop from aggressive/combat situations... but still...
The new system makes it much more "believable" as it requires additional sensors and points of input to become effective. (the more people equipped with P-tacs, the better the bonuses as you are now co-ordinating multiple references to gain a better tactical understanding of the surrounding situation.)
And, it wouldn't be the first thing that has been changed, or removed due to a better understanding of actual science and technology.. especially when that Science and technology directly contradicts what has been published.
Keep in mind too, Shadowtech came out what, 20 years ago? What was science fiction then, has become Science fact now in some cases, and the 2 just don't mesh at all and can create a disconnect in people with more direct knowledge of these things.
Heck, there is a small but vocal portion of the community that can't wrap their minds around the fact that SR diverged from our world radically in the 1980s, and constantly say "well we have 'X' now, so SR should also have 'X', but better!!" where X is everything from some "human right" to some doohickie piece of tech.
But if you really want it, there are ways to handle this. They are homebrew solutions, but possible. My GM has had to deal with this issue with our party as all our characters are continuations from 1e, which has lead to him having to deal with pieces of tech from 5 editions worth of updates, changes, reconfigurations, cost adjustments (both essence and $$$) and functionality.