I found this true for Sram power links... but when I switched over to KMC chains, and used a missing link... no amount of twisting, pinching, swearing unlocked it... hence why I had to DIY/buy the proper tool.
as ducky said... the installer tool isnt nessesary... just position the link between the cassette and chainring at the top, hold the wheel in place, and apply pressure to the crank arm.
edit: was google imaging earlier, but cant find it anymore.
I came across a picture with a piece of metal shaped like an 'M' ....I imagine once its been slotted between the rollers with enough downwards pressure, it will push the rollers together and unlock the link....
might try and making one on the weekend!