Because they are all incuse mold designs. The notation is required in TCR only where there two styles of a mold and they might be confused. Also, there are some chips that were made with an incuse mold for the casino and later reproduced for collectors in a flush mold. These were all molds with various combinations of dice, cards, and suits as I recall.

By the way, the word is "incuse", despite the use of "incused" in The Chip Rack. The word is an adjective, not a verb. There is no verb "incused". Here's what Webster says about the word:

Pronunciation: in-'kyüz, -'kyüs
Function: adjective
Etymology: Latin incusus, past participle of incudere to stamp, strike, from in- + cudere to beat -- more at HEW
Date: 1818
: formed by stamping or punching in -- used chiefly of old coins or features of their design