Looking upto the ceiling you can still has the original stone supports that hold the floor beams however these beams like the great hall are a new addition.
They would have been possibly replaced in the early 1900s with what you can see today, however since the 13th century they will have been replaced many times due to rot, fire and insect infestation like woodworm.
The lower and upper floors of a castle including this one have stone floors but all the middle floors like the bedroom above have wooden floors. The main reason for this was due to costs but also possibly to maintain heat as wood holds heat in but stone is more cold.
Typically, hardwood flooring was not just about aesthetics, but installed for practicality. Since oak and pine were readily available, those species are the most abundant in homes and castles from the middle ages.