The bug

Bed blocks do not cull against other blocks. This means that if a bed block is standing on top of full blocks, the bottom of the bed's feet will still be rendered, even if they're not visible, which is a waste of performance. It gets even worse if you put blocks around the bed, as then the northern/eastern/southern/western faces of the bed will also still be rendered despite not being visible from any angle, which also wastes performance for no reason.

While the performance impact is very minimal (especially if you only have 1 or 2 beds), it still exists, which is not good. (On a semi-related side-note, the top part of the "feet" are also rendered, despite being inside of the bed and thus always invisible, which likewise also causes an unnecessary (minor) performance loss.)

This is directly caused by MC-122532 being "working as intended". Despite that issue being "working as intended", beds not culling against blocks is definitely not intended, as it causes beds to render sides that should never be visible in the first place in some circumstances (including a very common one, being having a bed on top of a floor).