Custom heading options classes being stripped on save unless style definitions exist

Description

Using a custom config, if I set a custom heading option ("subtitle" in this example), the view class I set is being stripped on entry save. Disabling or enabling the "Purity HTML" option on the field has no effect.

https://user-images.githubusercontent.com/1728770/234957441-61147d30-a302-4448-9126-6e9e1e522b3b.mp4

Oddly, if I create a style definition and add the style selection option to the toolbar, the classes persist on save as expected (for both the heading option alone, and a paragraph set to the subtitle style.

https://user-images.githubusercontent.com/1728770/234958687-631d622f-ca03-4dea-8f7d-e28efa4f76fd.mp4

Config is as follows:

return {
    heading: {
        options: [
            {
                model: 'subtitle',
                view: {
                    name: 'p',
                    classes: 'ck-heading_subtitle'
                },
                title: 'Subtitle',
                class: 'ck-heading_subtitle'
            },
            { model: 'heading1', view: 'h1', title: 'Large Heading', class: 'ck-heading_heading1' },
            { model: 'heading2', view: 'h2', title: 'Small Heading', class: 'ck-heading_heading2' },
            { model: 'paragraph', view: 'p', title: 'Paragraph', class: 'ck-heading_paragraph' },
        ]
    },
    style: {
        definitions: [
            {
                name: 'Subtitle',
                element: 'p',
                classes: [ 'ck-heading_subtitle' ]
            },
        ],
    }
}

I would like Subtitle to be a heading option, not a styling option, but have its class persist on save. Am I misunderstanding how to configure CKeditor, or is this a bug?

Steps to reproduce

Create a custom heading option with a view object containing classes
Apply heading option in rich text editor field and save

Additional info

Craft version: 4.4.8
PHP version: 8.1.13
Database driver & version: MariaDB 10.4.27

Plugins & versions: CKEditor 3.2.1

"craftcms/ckeditor": "^3.2",
"craftcms/cms": "^4.4.0",
"doublesecretagency/craft-cpcss": "^2.6",
"mmikkel/retcon": "^2.6",
"nystudio107/craft-imageoptimize": "^4.0",
"nystudio107/craft-minify": "4.0.0-beta.2",
"nystudio107/craft-retour": "^4.1",
"nystudio107/craft-seomatic": "^4.0",
"servd/craft-asset-storage": "^3.3",
"spicyweb/craft-neo": "^3.7",
"verbb/field-manager": "^3.0",
"vlucas/phpdotenv": "^5.4.0"

craftcms / ckeditor