I got the exact opposite from that passage:
pg. 38. "Make sure to apply a relevant effect before comparing hits with the opposing dice. Only one Shadow Amp can affect a roll’s outcome; if two or more could apply to the Test, you must choose one effect to apply."
Those effects are things, "such as allowing the reroll of dice that failed to score a hit or reducing the number of opposing dice rolled, negating hits, adding pips to dice (that is, making the roll one number higher), and so on."
The only exception I found (which kind of reinforces the rule) is for Datajacks and Control Rigs, "Accessing the Matrix via AR does not confer any bonuses, but going full VR confers a +1 bonus to any Hacking Tests. This bonus is noted on Shadow Amps that allow VR connection, such as datajacks and trodes, and it always applies in VR, even if another Amp is used to affect a Test while in VR."
Of course, anyone can play this anyway that they want. The group gets to decide all that. so... meh?