Every time I try to break a mature beetroot plant in creative mode, it drops nothing. When I break mature beetroot plants in survival mode, it drops beetroots and sometimes seeds.
Beetroots do give drops when broken by water or when I break the farmland they're planted in, though, in creative mode.
Which is exactly how all other crops work, and have worked for some time. Blocks aren't generally supposed to drop anything when broken by players in creative mode.