9/11
Later in BIP34 a new rule was added.
Each coinbase TX is to include the height of the block.
As each block height is different, this guarantees each coinbase TX ID will be unique.
Blocks with such coinbase TXs are version2
Last version1 block was 227,835 was mined in 2013

10/11
This was a problem because it was not the desired behavior for Bitcoin TXs.
In some cases could have led to network splits.
Plus, could allow for some attacks, where you can reduce the confirmation of a TX to 1, making it more susceptible to double-spending.
(could****)
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