Im not a real pilot, but I can share my 2 cents about this.
When landing with very strong headwinds, and high temperatures, your wind correction values to the Vref speed are a lot higher. Hence, you run into the speed limitations of the high flap settings. In a 738-800, normal landing config is Flaps 30/40. However, should you face strong headwinds (i.e. 30ktG45kt), you are at the maximum recommended wind correction of VREF + 20 kts. At this speed, you will be in the red during F30 and F40. So an abnormal F15 might be the case.
So you were right in your thinking. Now if a RW pilot wants to come here and totally destroy my answer and shed sone light.... please do!
Nico