Note that some startups cross multiple categories. For example, a new type of computer display may need novel material, changes to a semiconductor process, and a delay for design-in as a component. While some can be done in parallel, some cannot, so you could end up slower than the slowest step.
While medical drugs may be the slowest to revenue, it might not actually be the slowest to a liquidity event because once you pass some of the initial stage-gates, there is a liquid market to sell the company pre-revenue.