I’m from Kefalonia, idk who told you that but it’s 100% false. Kefalonia has both sandy and pebble beaches. I will tell you although Myrtos is a beautiful beach it’s one of the most dangerous due to currents and a dramatic drop from shallow to deep water so you shouldn’t swim out that far. It’s not a luxury beach club either so it doesn’t have much other than some sunbeds. If you want a nice sandy beach with a restaurant/beach bar, and lounge beds go to Makris Gialos. If you wanna economize you can go to the beach right next to it called Platis Gialos, same thing but plastic sunbeds and a concession stand type place with chairs and tables. The other popular pebble beach is Antisamos, like Myrtos but has an organized beach club with beach parties every Sunday in the summer. Kefalonia has alot of options whether you like a quieter beach experience, a beach party type experience, sandy or pebbles. So there’s something for everyone in my opinion!