How to customise Ionic v4 SCSS variables (NOT the CSS variables!)

I don’t understand what the go is with styling in Ionic V4.

Yes, I get that it now uses CSS variables, and I can see all the options for customising components with CSS variables in the documentation.

That is not what I’m talking about. I’m talking about the SCSS variables here:

// iOS Input
// --------------------------------------------------

/// @prop - Font size of the input
$input-ios-font-size:                     inherit !default;

/// @prop - Margin top of the input
$input-ios-padding-top:                    $item-ios-padding-top !default;

/// @prop - Margin end of the input
$input-ios-padding-end:                    ($item-ios-padding-end / 2) !default;

/// @prop - Margin bottom of the input
$input-ios-padding-bottom:                 $item-ios-padding-bottom !default;

There’s literally hundreds of them, and I’m not seeing any way to customise them.

I want to change $input-ios-input-clear-icon-svg to use my own custom icon, and I can’t see how I would do that. Setting that variable myself is not having any effect.

There is literally no mention of all these SCSS variables in the documentation, it’s as if changing SCSS variables is not supported, and all we are allowed to do is modify the CSS ones. The CSS variables do not cover everything… so that doesn’t make sense to me.

Am I just doing something wrong, or is this not possible?!