Fermacell dry screed on expanded clay pellets?

Hello, I am currently renovating my bathroom and came across the alternative dry screed. My original plan was to reuse or supplement the expanded clay aggregate I still have. Back then, these balls with a diameter of about 0.5 - 1 cm were used as aggregate. I have a quite large aggregate height of 20 cm! Now to the question. Can I lay Fermacell dry screed boards on these expanded clay balls? The plan would then be to finish the floor covering with 60x30 cm tiles. Thank you for your tips

Basically, this is possible if the filling is intended for it (such as fillings from Fibotherm). It must therefore be pressure-resistant and not a pure cavity filling.