Does anyone have more detail why the Type 1 gold dollars were recalled, prior to the Type 2?

As I write these words, I am in my hotel room in Houston, looking out the window. On this, my first visit to Texas, I am finding that everything is BIG here. For example, I am looking at a BIG convention center, several blocks long adjacent to my hotel, across the way is the BIG Minute Maid Center, across the street is a BIG garden, smack dab in the middle of the city (you don't get block-long gardens in Manhattan), and there is even a BIG bar called The Grove across the street (I am not sure why it needs to be so large, but I have stopped questioning things in Texas). If I look beyond the convention center, the land is as flat as a pancake, and I can see to the horizon.

On my flight down, I continued to read QDB's Gold Dollars book. In the book he writes,

"The San Francisco Mint opened in the spring of 1854, just in time to coin one variety of the Type 1 gold dollar, the 1854-S. In August, 1854, whent he first shipments of the Type 2 dollars were made, the Treasury Department because to call in the earier small diameter Type 1 coins minted since 1849. This does not seem to have applied to the 1854-S coins circulating in remote California. By 1861, approximately 8,000,000 pieces had been redeemed, amounting to more than 60% of the Type 1 issues."

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(1) Does anyone know the reasons why the Type 1 coins were recalled, rather than remaining in circulation? I don't think there was a shortage of gold.

(2) What was the theory behind not including the SF coins in the recall and melt?