If a pilot uses an inappropriate technique (not using IAS for example) for the situation, he has made an error of judgement or possibly a cognitive error - that appears to be what happened at the beginning of the approach and should not result in a fatal accident.
But, when the ramifications of that judgemental or cognitive error become apparent (aircraft deviating from flightpath), the real pilot error is not flying the aircraft first and foremost.
Failing to take the required corrective action in a worsening situation until it is far too late isn't a procedural, legislative or technical failure - it is pilot error, no matter how much of a nice chap he might be.
Sorry, but despite TCs failings as a 'pink and fluffy, keep everyone happy bunny'
I think he has called it correctly.