What you call 'sedimentary volcanism' is not the same as true volcanism. True volcanism is the eruption of molten rocks (lava, or rock above its melting temperature); sedimentary volcanism, which geologists are familiar with, is the intrusion or expulsion of a suspension of sedimentary material
below its melting temperature and water, driven, as the Dictionary says, by gas under pressure. Sedimentary volcanism produces mud volcanoes, sedimentary dykes, and outbursts of water and sand from fissures during earthquakes.
There are resemblances in the eruption mechanism of true volcanism and sedimentary volcanism, since both are driven by gas under pressure, but that does not make lava (molten rock) a sedimentary rock.
Yes, there is evidence that about 3.5-3.3 billion years ago (during the Archaean era) there were no continents and the Earth was effectively a water world. There may have been small volcanic islands, but there were no continental land masses. However, U-Pb dating of zircons from Archean sedimentary rocks in India -
Earth's 1st continents arose hundreds of millions of years earlier than thought and
https://doi.org/10.1073/pnas.2105746118 - has found evidence that the continental cratons began to emerge from the global ocean around 3.3-3.2 billion years ago, more than half the age of the Earth.
The water-world stage of Earth history therefore has nothing to do either with Noah's flood or with the creation story in Genesis 1.