DXC ignores struct cast when writing to an AppendStructuredBuffer

Repro:

struct I32 { int value; };
struct F32 { float value; } f32;
AppendStructuredBuffer<I32> output;
void main() { output.Append((I32)f32); }

DXC output (shortened), note the lack of fptosi:

%0 = call %dx.types.CBufRet.i32 @dx.op.cbufferLoadLegacy.i32(i32 59, %dx.types.Handle %"$Globals_cbuffer", i32 0)
%1 = extractvalue %dx.types.CBufRet.i32 %0, 0
call void @dx.op.bufferStore.i32(i32 69, %dx.types.Handle %output_UAV_structbuf, i32 %2, i32 0, i32 %1, i32 undef, i32 undef, i32 undef, i8 1)

FXC output (shortened), note the ftoi:

ftoi r0.y, cb0[0].x
store_structured u0.x, r0.x, l(0), r0.y

Note that it does not repro using an RWStructuredBuffer, so it probably has to do with the append intrinsic.