Of course that you still get the error when you do it via the browser. It's not meant to do that for such an amount of products and that's why I recommended you to use the new options to generate the XML files automatically so that you can just have a download link for the xml file.
It's not really a matter of HikaShop. No matter what you do, having a process loading 50 000 elements with all their information (prices, discounts, variants, images etc) on one single PHP process requires a lot of resources.
On a normal products listing on your website, you display 20 products at once with a pagination to see the rest so 50K products is not a problem. But here, the system has to load everything on the page, and that's why you get that resources issue. Normally, with so much products, you wouldn't generate the XML dynamically each time someone request it. Instead, you would have it generated automatically once every day and then provide the link to the file (the same method I recommended in my previous message).