My A6 Bi Tdi went for a service yesterday, + an MMI failure, I got an update call and they told me they have applied the Turbo repair kit for the recall.

Until that point I had no idea there was a recall, I asked what it entailed and was told it was nothing just some improved parts fitted inside the turbo, the advisor was clearly reading notes and not technical.

Are any other Bi Tdi owners aware of this recall, with insight to why it's required?

I can only presume some cars have had failure, with high risk of warranty claims costing more than a recall for all affected vehicles. I'll ask for more details and the recall technical advisory notes when I collect.