Instant decline would be a better situation than hard pull and decline. AMEX has unique and less harmful way of declining existing customers which is pretty nice. Unless any of those information is wrong (you didn't open some cards but reported that way, or your income is higher that what they have, etc), you'll get declined anyway. 10 cards for 12 months is too much from any aspects. Now that churning is impossible, I would wait another 2-3 years for the same deal to appear.