Why is a sotāpanna defined as unable to take another teacher and unable to commit matricide?

Among the descriptions of stream-enterer (sotāpanna) is one which says that they is not capable of committing [six wrong actions](https://en.wikipedia.org/wiki/Sot%C4%81panna#Six_actions_that_cannot_be_committed) : > - Murdering one's own mother. - Murdering one's own father. - Murdering an arahant. - Maliciously injuring the Buddha to the point of drawing blood. - Deliberately creating a schism in the monastic community. - Taking another teacher. Question: 1. **Do the scriptures and/or commentators say something** about the significance of this particular selection of actions? Why are these (and not some other) actions the ones which cannot be committed? 2. Is it suggested hereby that **creating a schism** in the monastic community **is as grave an action** as patricide, matricide or murder of a holy and peaceful person? 3. Does it also mean that taking another teacher **is like wounding one's teacher**, which is as terrible an offence as patricide, matricide, murder etc?