Eureka!!! The value can be accessed like this : e.target._input.value. This is how it works :
<mwc-textfield on-input=${e => this.inputValue2 = e.target._input.value}></mwc-textfield>
Found it here: https://github.com/material-components/material-components-web-components/issues/48
It was not the POST I was worried about. I couldn’t take inputs from the granular components to the top level ones. The ones who are writing mwc-testfield are also trying to give a better solution. However… problem solved.