It's not required but recommanded. The main difference is that the first synchronization of the blockchain will take much longer (unless you download it separately, but it's not the native way of doing it with Umbrel: https://umbrelinfo.gitlab.io/faq.html#can-i-use-previously-downloaded-blockchain-to-save-time-when-setting-up-my-umbrel-node ).

To give you an idea of the order of magnitude, with an SSD that would take about 3-4 days, with a HDD it's more like 3-4 weeks.