magento2: Why doesn't shipping total segment respect tax settings like e.g. subtotal does?

Created this patch, use with precaution however as this is only tested with Including tax config settings…

--- a/vendor/magento/module-tax/Model/Sales/Total/Quote/Shipping.php	2020-10-28 10:15:59.000000000 +0200
+++ b/vendor/magento/module-tax/Model/Sales/Total/Quote/Shipping.php	2020-10-28 10:16:44.000000000 +0200
@@ -72,12 +72,22 @@
      */
     public function fetch(\Magento\Quote\Model\Quote $quote, \Magento\Quote\Model\Quote\Address\Total $total)
     {
-        if ($total->getShippingInclTax()) {
+        if (!$total->getShippingInclTax()) {
+            return null;
+        }
+
+        if ($this->_config->displayCartShippingBoth() || $this->_config->displayCartShippingInclTax()) {
             return [
                 'code' => 'shipping',
-                'shipping_incl_tax' => $total->getShippingInclTax()
+                'shipping_incl_tax' => $total->getShippingInclTax(),
+                'value' => $total->getShippingInclTax(),
+                'value_incl_tax' => $total->getShippingInclTax()
             ];
         }
-        return null;
+
+        return [
+            'code' => 'shipping',
+            'shipping_incl_tax' => $total->getShippingInclTax()
+        ];
     }
 }

For subtotal there seems to be own logic inside: \Magento\Tax\Model\Sales\Total\Quote\Tax::fetch line 341

        /**
         * Modify subtotal
         */
        if ($this->_config->displayCartSubtotalBoth($store) || $this->_config->displayCartSubtotalInclTax($store)) {
            if ($total->getSubtotalInclTax() > 0) {
                $subtotalInclTax = $total->getSubtotalInclTax();
            } else {
                $subtotalInclTax = $total->getSubtotal() + $taxAmount - $total->getShippingTaxAmount();
            }

            $totals[] = [
                'code' => 'subtotal',
                'title' => __('Subtotal'),
                'value' => $subtotalInclTax,
                'value_incl_tax' => $subtotalInclTax,
                'value_excl_tax' => $total->getSubtotal(),
            ];
        }

This logic however is missing for shipping reader

Hello All

I am not able to reproduce this issue on the 2.4-develop branch by provided steps.

Testing scenario:

1. Choose “Including Tax” setting for Display Shipping Prices and Display Shipping Amount.
2. Create a (guest) cart
3. Call /rest/V1/guest-carts/<the_id_here>/totals-information for the cart

Result The value property for shipping segment in responseData.total_segments includes the tax. So I have to close this issue. Thanks for your report!