Variable Current Lead Acid Battery Charging
The short answer is - NO!  No need to waste power from the panels.

You are correct, the lead acid batteries are best charged on a CC-CV logarithm. However, constant current doesn't mean that the battery has to be fed an exact pre-determined current or the battery suffers.  It would be better interpreted as a maximum current that the battery can be charged at.

In an ideal world, where lead acid batteries worked better, we would just apply the voltage at the level of the constant voltage and let the current flow in until it saturated.  Unfortunately,  if we did that with lead acid batteries currently being produced, the current flow at lower charge levels would be so high that they would fry the battery.  As a solution, the charge starts at a constant current level that is lower until the battery starts to fill up to the point where you can apply the constant voltage voltage and the current at that point won't be too high because the battery is already fairly full.

So if that made any sense, you should be fine to charge the lead acid battery at a lower and uneven current in the constant current stage of charging as long as the current doesn't exceed what the manufacturer recommends for the battery that you are using.

Specifically to answer your question, charging at lower current doesn't hurt the battery (unless the current is so low that the battery never charges because self discharge is greater than the charge current!).