Net Promoter Score was designed to measure loyalty to a company — a relationship — not the quality of a specific interaction. Using it to guess training quality at micro-scale misuses the instrument. And if you change the question, you break the validity: asking something NPS-ish is not the same as asking the exact NPS question, so I don’t recommend “NPS-type feedback” for learning at all.
There’s a practical trap too. Scores can be gamed without improving anything. Take two identical training courses and add a hot lunch to one — which gets the higher score? Will the learning outcomes differ? If NPS is your metric, you may end up promoting courses that make people fatter rather than more capable.
What I prefer to ask instead is simple: “Was this a good use of your time?” It respects the learner, it maps to the thing that actually matters — whether the intervention was worth the time invested — and it opens a more honest conversation than a 0–10 recommendation scale ever does. The full article covers the background, the evidence and how I use the question in practice.