What I think you have misunderstood is that those ads are not stored on the BF server, they come from ad networks.

Cookies are present on every site you visit, and without them your device/computer browser wouldn't remember where you went and take you back, all your login details wouldn't stick and stuff wouldn't work. Cookies are not evil, and even if you browse 'anonymously' your ISP and the site know you were there. There is no real anonymity for most.

So loading ads is only as fast as they can be retrieved from the network.

And how they load on your mobile device/phone is going to be different from how they load on a PC. Different operating systems/browsers, the method how they get to your phone, all are different. The platform has to be written to display on all of these devices as well as PC and Mac.

The only way they could be equal between the different systems is if your mobile device had the same aspect screen and a decent size for viewing.

Phones are too small for that so you'll always get 'pan and scan'..there is no way around this...unless you use a PC or laptop, maybe a tablet.