Uh-oh, there is a giant difference between an all-purpose browser (which you can choose) created by an unrelated third party and a client forced onto you by the store's owner.
Like I said... it's a mental/technical difference... still need a "piece of software" to log in and download your games... you can try and beat around the bush, but that's just a fact
I dread throwing myself into yet another argument about what constitutes DRM, but I have to point out the small but important distinction here: the having to install a specific bit of proprietary software to not only download, but to install the piece of software that you actually paid for is functionally the same as DRM. Whether you want to go the full measure and actually use that term is irrelevant. If I buy a game that has a DRM-free download (whether it be a GOG-style installer, or just a compressed archive of the game folder), I can download it via whatever current browser I choose, and install it immediately, or install it at any time later, even on a different computer, as I wish. If buy a game that has a required proprietary management application, I can download and install the game now, but I have no option to download now and install later when I'm offline -- the installation is a streaming one. (Steam has a not-very-well-publicized stripped-down command line version of the client that is apparently just a downloader for the game files...but it's telling that it's still a separate software client, rather than just a feature that they built into their website.)
Making the "you need a browser to download your games, therefore browsers are DRM" argument shows more concern with not "losing" the argument than with thoroughness of thought. Put another way: you confuse literal, physical requirements
(e.g., needing some kind of web browser software to access the Internet, needing some sort of DVD/media player to watch a DVD) with arbitrarily imposed "requirements" (e.g., needing a specific piece of proprietary software to be able to access or use otherwise self-contained software) at your peril.