In section 7.4.3.3.1 of HEVC SCC draft 3, the semantic of constrained_intra_prediction_flag is as follows:

"constrained_intra_pred_flag equal to 0 specifies that intra prediction allows usage of residual data and decoded samples of neighbouring coding blocks coded with or without using a reference picture that is not the current picture. constrained_intra_pred_flag equal to 1 specifies constrained intra prediction, in which case the general intra prediction process only uses residual data and decoded samples from neighbouring coding blocks coded without using a reference picture that is not the current picture."

However, there is ambiguity about the definition of "general intra prediction". It can be interpreted as either intra prediction only or intra and IBC prediction. In current SCM-4.0, it should refer to the second case, i.e., intra and IBC prediction. It is recommended to improve the text to match SCM-4.0.