The key to uploading multiple images at the same time in this method is to match the image file names to the product SKU. There is also a configuration area to specify the separator. The image file names should start with the Product SKU, followed by the separator, followed by the order number of the image related to the other product images for this specific product.
This extension is successfully working on Magento stores with large catalogs, some have over 20,000 SKUs and each product have 3-5 images. Even if you have only a few hundred products, this will still save you a lot of time. The system also offers importing all images, or importing new image files only for those cases that you only uploaded 2-3 new images and do not want to update the entire set of images. This extension also works very well with CDN and stores behind caching mechanisms.