False.
Assume a bad miner controls 25% of the network.
Coin A has a 1 minute block time
Coin B has a 10 minute block time.
After 2 blocks, there is a 1 in 16 chance the bad miner can double spend
After 3 blocks, there's a 1 in 64
After 4 blocks, there's a 1 in 256 chance.
4 minutes with coin A for that chance, 40 minutes for coin B.
No, its not that simple, please do a bit more research. There are good reasons 10 minute target was chosen:
https://bitcointalk.org/index.php?topic=232297.0