I believe if you create a layer style preset the Adobe store the resolution of the document that you were editing when you created the preset into the preset so Photoshop can scale the style effect to the resolution of the document you apply the layer style preset to.
Layer style setting as you know are in terms of absolute pixel. That would mean the size of the shadow would vary on document that had different resolutions, Notice in menu layers there is Layers>Layer Style>Scale Effects... and In the Image Size dialog(s) there is a check box Scale Styles or a setting Scale Styles..
If it working differently in CC version 15 then is was in CC version 14 they may be a new bug.
If you want a 7px drop shadow no matter what the documents resolution is you may be able to record an action that add a 7 PX drop shadow using the Layer Style dialog not using a preset style.
I created a Drop Shadow Preset on a 300 DPI Document distance 2 px size 7px. I then recorded an action the applied that preset and then applied the same settings using the layer style dialog instead of the preset. There is a great difference on how the two steps were recorded.
When I step through the action on a 300 DPI document the drop shadows looks the same. On a 72DPI document the Preset drop shadow looks small like the 300dpi document however the step that was recorded with the Layer Style Dialog the layer drop shadow looks much larger for it was not scaled down to match the documents 72DPI resolution.
So it look like if you use a Layer style preset from the style palette the effect will be scaled for the documents DPI resolution. Notice in the action there is a Layer Style Scale 100% in the step recorded using the layer style dialog. Where the preset DS is applied some how by Photoshop and Photoshop scales the effect....
Thank you so much for the idea about creating an action. That's a great idea! I'll definitely go that route!
And thank you also for the thought about the the resolution effecting the drop shadow size. I didn't know that. I think, though, that the resolution has been the same throughout. I'm doing screen captures using Snagit, so I think that the resolution of the images that I was using before the update to 2014 CC are the same as those I'm using now. So it seems to be working differently somehow. Maybe it's a bug?
Either way, though, you have given me a great workaround. Thank you so much!