@Jim as @Evgeni_Popov said the playground is an area for users to try out coding in Babylon.js, give live code to get help in the forum and also to provide working examples in the docs. The docs themselves are open source and can be added to via a PR by interested users and so can vary in writing styles. However you are talking about the playgrounds after they are downloaded rather than the contents of the playground themselves.
A playground gives users the opportunity to try out and concentrate on Babylon.js without worrying about the the HTML and JS code needed to get it to work on the web, initialise the engine etc. all this is done in the background. The minimum wrapper to make a playground into a working web page can be found at Getting Started - Chapter 1 - First Web App | Babylon.js Documentation.
When you download a playground a wrapper, to turn it into a working HTML document, is automatically added and the formatting of the automatic code may not match the user written code. Downloading a playground provides you with the scripts needed to quickly view the code locally and to edit the code as you wish. It is not meant as an example of a fully formatted code layout. For example, having downloaded a playground, you might want to try out your own function to create the engine with a different set of parameters. You can then do that easily by adding your own createMyEngine function and the code that repeats createDefaultEngine then becomes
initFunction = async function() {
var asyncEngineCreation = async function() {
try {
return createMyEngine();
} catch(e) {
console.log("the available createEngine function failed. Creating the default engine instead");
return createDefaultEngine();
}
}
This way if your create engine function fails the default engine will still load.
When you add to or edit a playground and then save it, its reference key at the end of the URL increases by 1 so a series of similar playgrounds may have much of the code in common see Playground | Babylon.js Documentation
Hope that answers some of your questions.