Just got the 75k offer on my iphone, using the mercury browser and was approved. I tried using all the major browsers on my mac and windows machine and wasn't able to get above 50k.
Some extra datapoints: I currently also have the mercedes amex platinum that was applied for earlier in the year, as well as 4 other amex cards. I previously had this same gold amex business card, but have had it closed for about 2 years.