No! Vertical soffit is not a gable vent nor does it provide any ventilation for the attic. And this is why...
This triangle vent size is porportionate to the gable and attic space to be vented. The problem is the blockage caused by the almost solid panels restricting the airflow.
The tiny perferations in the perferated soffit panels is designed for cornice or overhang use, not gables. Gentle breezes will enter the tiny holes but heat needs a lot more open space to properly escape. In most cases, these panels will distort or melt under these extreme heats. Once the soffit panels start to heat warp, they will bow outwards and become loose in the j channel. Eventually they may fall out. Preferably before causing the attic to catch fire. This is why it is so important to use metal gable vents designed to vent the maximum amount of heat the quickest from the attic. Another issue with perferated soffit vents can be dust. Just a tiny amount of dust can clog these minute holes and prevent breathing completely. When vinyl siding installers install vertical soffit vents, they may actually endanger you and your home. More attic fires start from improper ventilation than one might think. If you notice a drastic change in your heating and cooling throughout the year, it may be your home warning you your attic is not breathing correctly and is not happy.