When a mob dies on top of a partial block, such as a carpet or half-slab, it does not convert nearby sculk-convertible blocks to sculk.  As per Gnembon's explanation from MC-249233, this is intended behavior.  However, if the partial block is on top of a sculk-convertible block (such as stone), and is directly next to a sculk block, it will convert the stone beneath the partial block. 

Steps to reproduce:

1. Build a platform of stone with a sculk catalyst within 8 blocks
2. Cover one of the stone with carpet or another partial block
3. Place a block of sculk directly touching the covered stone block
4. Drop a mob to its death on the carpet

(See attached picture labelled CarpetStoneConverts)

Expected result:

Sculk to be created but the carpeted stone would not be converted.

Observed result:

The carpeted stone is converted to sculk.

Notes:

I have heavily edited this bug report to take into account Gnembon's explanation, this will explain why the comments appear very disconnected from the report.