The q1 on-demand metrics are definitely very interesting!

One possible cause of this trend is actually still consistent with spot demand growth in aggregate: when customers deploy spot fleets with on-demand backup capacity and all spot prices get closer to on-demand, those fleets would become more likely to revert to on-demand, rather than a more expensive pool of spot instances.

Measuring this would be a great opportunity to leverage the vantage point that your team has!