Solar panels only produce on average 77% of their rated output when they are under direct sunlight because the sun heats the solar cells up to around 160F which causes the solar cells produce less than their rated power output. Solar panels output ratings are calculated based on perfect artificial sun and 72-degree room temp FYI.
So 2w worth of panels x 77% Heat loss = 1.54 watts of power output under perfect conditions.
0.912 watts from you 2 watt solar array under normal weather conditions which is probably to be expected if you're not seeing direct sunlight on the panels and the solar cells in the panels are probably not the best.
Sometimes the Electron can limit charge current depending on how charged the battery is.
You may be getting more current into your battery if the PMIC is down converting the higher input voltage to the lower battery voltage.
Its always better to go with a larger panel due to inefficiencies.
This is common to not 100% SOC due to the fuel gauge setup.