The progression chart shows how laptimes are recorded through the session. The ordering is not faithful to the ranked overall classification, and the gap times do not correspond to gap times given in the final classification. Instead, they are based on the best recorded laptimes measured across the whole session. (For example, you can see this in Q3 where some drivers do not improve on their Q2 times.)
Here's a view of the session utilisation with rows ordered by overall classification and colouring relative to each separate round of qualifying:
How did the cutoff time evolve in Q1?
PS Hmmm....seems like the FIA website is giving random results compared to the official timing sheets?
For a corrected version of the chart, and a view that shows the laptime progression across qualifying sessions, see F1 Spain - Qualifying progression chart (corrected) and Q3 "grid".
Code describing how to create the evolving cut-off time will appear in a forthcoming chapter of Wrangling F1 Data With R.