I have managed and written tooling for RDBMS from dinky GB-sized up to the multi-thousand-shard PB-scale. What you're saying is absolutely true. What a small team with vision can do when they see the ramp coming pays off 100-fold just a year or two in the future.
I think this kind of anticipation was part of Pinterest's early success, for example. They got ahead of their database scaling early and were able to focus on the product and UX.