During descent, update the fix you are flying to about every 2000 feet. Vertical path solution is calculated with minimal disruption to the path descent based on FMC computed winds and current anti-ice configuration.
I don’t know… trying to trick the system by selecting phantom altitudes on the MCP??? Watch out for mister level bust with this technique in high density areas of frequent frequency, heading and altitude changes. Is this SOP??? who know? Remember... KISS