Exclude OU not working

I have this code that will get all users from AD

$old = (Get-Date).AddDays(-90).ToFileTime()

$ldapFilter = '(pwdLastSet<={0})' -f $old

Get-QADUser -LdapFilter $ldapFilter  -SizeLimit 5000

This returns 1,300 users.

But when I run this it too returns 1,300 users

$old = (Get-Date).AddDays(-90).ToFileTime()

$ldapFilter = '(pwdLastSet<={0})' -f $old

 Get-QADUser -LdapFilter $ldapFilter  -SizeLimit 50000  | Where-Object {$_.DN -notmatch '_TRAIN'}

We have about 200 users in TRAIN so I should only see 1,100 users.   Both pieces of code run fine without errors.  How come the exclude is not working?