When I applied for my Disney Visa, over 6 mo. ago, I got a message that I was approved for $5000 and I would receive my card within 14 days. (I applied online). When I received my card, the limit was $15,000. I called Chase to activate the card and ask about the difference in my initial approval amount and the final credit limit. I was told they do a more thorough check on your credit history before making the final determination.
Based on my experience, I guess they just eliminated the initial approval step. I'm sure they are saving money, somehow. But it did take about 2 weeks to receive my card.
DH applied for the Southwest CC, also from Chase. He applied about 2 months ago. They didn't give us an initial approval notice and it took the full 2 weeks to hear back from them.
LONG STORY SHORT: Your experience sounds very typical to me and shouldn't create worry.