I've played thru 90 or so in mame getting 10k drops every round, it can be done but there are subtle difference in each round that make it pretty difficult to execute in a real game. Good work so far.
Those little differences on some rounds are an execution issue for sure.
For example...these starting rock drop patterns below work for Round 33-137+ but it's a lot more to keep track of than going to the left like we usually do. Also some of the later patterns are pretty tricky to do consistently. You also end up with two fast angry Frygars coming at you on top of each other on some of these later rounds right after the drop (97+).
Round 33-137+
*Note* on Rev 2 with no slowdown rounds the Round 137+ starting rock drop works up to the kill screen without any changes

The background for most of these is from older screenshots I took of a quicker but more pumpy dirt clearing pattern that balances speed versus all the earth points. The first rock drop is what matters here. Pooka's are blue and Frygar's are red btw for the few rounds I include monsters above. I only show what I need in these as a quick reference when playing and glancing at my phone.
I may make a compilation video of all these first rock drops to share later. Plenty of free time these crazy days...