A function that compares the commands listed in dbatools to the commands listed in the commands index page. No errorhandling.

Find-CommandDelta

using namespace System.Collections.Generic

 function Find-CommandDelta {
    param(
        $ModulePath = 'C:\git\dbatools',
        $Uri = 'C:\git\web\commands\index.html',
        $Exclude = @('Where-DbaObject')
    )
    end {
    
        if (-not (Get-Module dbatools)) {
            Import-Module $ModulePath
        }
        [hashset[string]]$commands = Get-Command -Module dbatools -CommandType Cmdlet, Function | 
            Where-Object Name -notin $Exclude | 
            Select-Object -Expand Name
        
        $CommandPage = 'C:\git\web\commands\index.html'
        $commandPage = Get-Content $CommandPage
        $pattern = '<a\ href="http://docs\.dbatools\.io/(?<command>.+)">(\k<command>)'
        [hashset[string]]$uriCommand = foreach($line in $commandPage){
            if($line -match $pattern){
                $matches.command
            }
        }
        
        # Clone hashset becuase ExceptWith modifies collection
        [hashset[string]]$missing = $commands.clone()
        $missing.ExceptWith($uriCommand)
        
        # Clone hashset becuase ExceptWith modifies collection
        [hashset[string]]$extra = $uriCommand.clone()
        $extra.ExceptWith($commands)

        return [PSCustomObject]@{
            Missing = $missing
            Extra = $Extra
        }
    }
 }

 $delta = Find-CommandDelta