SSDs do behave like complex block devices from the perspective of a database engine. However, SSDs are sufficiently different from spinning disk that optimal I/O patterns are not the same. Some high-performance database I/O schedulers have separate storage behavioral modes (approximately based on common SSD and HDD behavior) depending on the storage characteristics.

Everything on a computer approximates a block device. Even RAM is treated as a type of complex block device in sophisticated, high-performance databases, because it is. Scheduling operations to optimally match the characteristics of block devices is a (the?) primary optimization mechanism.