Surely the fact that the McLaren's best lap is a 1:27:691 should ring alarm bells. The fastest lap in testing last year was a 1:22:792 so unless they have been absolutely brimmed with fuel all day then its not looking great.
There would be absolutely no reason to trundle around slowly unless you couldn't go much faster. Surely they would want to get some fast(ish) laps in just to see the improvement if there was one?
Bit premature to be saying that surely? That 1:22.7 was done in the third week of testing last year.
This is the first day, when teams are mainly doing system checks.