1) concrete is 5k health and cobble is 1.5k, in A19 Reinforced concrete was 5k and reg concrete was 3k, you also don't have to wait for it to dry
2) removing the drying phases makes building stuff so much easier, I don't have to set and lay a whole bunch of building blocks and then wait for every single one of them to dry to upgrade them all.
3)meh
4) when I am trying to upgrade a base before horde night, or work on one in general, I really dislike that random amount of time I have to wait for it all to dry, for example if its a corner piece I would have to wait for it to dry and fully upgraded it before I could build on top of it , it added alot of unnecessary and annoying time bottle necks to making a structure with fully upgraded blocks. I prefer to min max my exp rather than just leave those pieces un-upgraded
I feel like in this case complexity results in tedium and time consumption, and not necessarily interesting player choices because if its a horde base I will always want reinforced concrete or steel, and this simplification makes that process far easier and less painful/time consuming.
Also, if I am working on a hordebase , there isn't alot to work on or do while I am waiting for the wet concrete to dry, and its boring to wait to upgrade stuff. aside from removing grass around the horde base I am not sure what else to do in that time