I'm just telling you how the courts and the law looks at the situation. I never said it would make sense to you.
The FDCPA does not define legal action as a collection activity.
The purpose for a request for validation is to say "prove to me that I owe you anything and what I owe".
But that is all made moot by the lawsuit. Now, you can file responses and requests for documents, etc., as part of the discovery that will satisfy your "prove to me what I owe or that I owe anything." Logically, you can get what you wanted from the validation. Right?
You can try to convince the judge that filing the lawsuit is a collection activity -- but don't expect to get far with that argument. This would be persuasive to a judge only if you had a precedent in that district -- maybe there is one but I've never seen it.
If this debt is a matter of dispute over facts, then you have the perfect opportunity to demand the plantiff prove their case and to present your case for how you've been wronged. That is what court is all about.
If, however, you just don't want to pay the debt and are looking for the FDCPA to "whoosh it away", expect a lot of disappointment.
If you don't file a response to the summons you will lose by default. There is nothing you can do to defeat a judgment except file bankruptcy.