Do people really use Windows as a production server for PHP? Most people I know use Windows as a dev machine, which I guess will still be supported.
Except they never do, because they don't know PHP on Windows either and are afraid of breaking things, and the customer ends up with a PHP/Wordpress installation that is 4 years out of date. Luckily, most of those are internal-only apps, but it still sucks.
Where I used to work, we developed and supported a SaaS app based on PHP with PostgreSQL and Apache. We had two self-hosting customers who ran on Windows Server with SQL Server for the exact reasons mentioned, and they were our most troublesome customers. Performance tuning (and hence regular complaints that 'our' app was horribly slow) was a particular issue - mostly due to their admins' lack of relevant experience on both the stack...and Windows Server(!). The whole setup was a pain because we got so much flak, despite the premise of 'self-hosting' being that the customer had sufficient smarts to support the infrastructure and stack and we'd just support the functional and development aspects of the app.
One customer also had the system so locked down that for remote admin we had to connect to a jump box via VPN + RDP and then jump from that to the server with another RDP connection. Fetching large log files through that setup was a challenge.
Partly for our sanity, we persuaded one customer to let us migrate them to a Linux server; that went very well and really cut down on angst all round even though we then took responsibility for platform support.
In my limited experience, this is the sales team saying 'anything' to get the sale.
The logic behind it was that the client had some other websites running on some .NET CMS (not .NET Core), so it made sense for them to run WordPress on the same one instead of getting another one.
Manufacturing Execution Systems run on Windows; when virtually all your servers are Windows because of the apps you need to run, setting up a few Linux servers for minor apps for internal use only is not worth, so PHP in fast-CGI more under IIS is a very simple and effective solution.
Having support people with good expertise on both Windows and Linux is expensive, having 2 separate teams in expensive (if you need high uptime), especially when the ratio Windows to Linux is just 10:1 or 20:1. Keep it simple, run PHP on Windows.
EDIT: I forgot to mention the pseudo-SSO called Windows Integrated Authentication that works with just a few clicks on Windows, probably a lot more key presses (typing) in Linux.
With Apache, it's an unstable mess. IIS on the other hand works extremely well with PHP, we've had virtually 0 issues in more than 10 years using it for many different projects.
IIS is fine if it works just like Windows apps generally are fine when they work its the odd time where it breaks that you are mystified about the whole thing.
I've found it to be pretty good using FastCGI.
And no, it probably wouldn't be WSL, it'd be using this. Because not everyone I work with is comfortable with Linux tooling and who knows if our management tools can see what's going on with it.
In a Windows environment, the best tool for the job is almost always another Windows box. Arguably, sure, PHP is a poor choice for a Windows environment, but IT/operations rarely has the luxury of deciding what line of business apps other departments use.
Main reasons familiarity started as a windows application developer, the gui in my case window explorer feels easier for the tasks that I need do.
I have setup webservers on linux as well, Just I work faster in windows can fix things easier then having to google with linux when things go wrong. I prefer the windows file permissions