[majorvices]

There are two conversations going on here: 1) you shouldn't make a starter with dry yeast and 2) a starter that is too small can actually be harmful to the overall yeast population. Regarding the former: this is well documented and not sure any more clarification is necessary. Regarding the latter, there is a lot going on here and, as Denny wisely and succinctly points out "It's not all about cell counts". For instance, if the yeast is unhealthy then--absolutely, a starter should be used and is beneficial. I'm talking about using fresh yeast in an undersized starter. And instead of writing a book I'm trying to keep it succinct (which is difficult because it is a complex topic).

Regarding the Yeast book by JZ and CW: It's been a minute since I read that book but 1) they aren't talking about dry yeast 2) I believe they are talking about pitching an active starter with liquid yeast (not growing yeast and fermenting the starter to completion). I'll also add that liquid yeast packaging has more live cells that it once had by a long shot. When I first started brewing in the mid '90s you needed a starter for any liquid pitch of yeast you purchased (and dry yeast was all garbage, lots has changed). I'm not sure what the cell counts in the packages of yeast were when the book was written. But I feel confident that if you emailed Chris White, and asked him if an undersized starter could be less-than-beneficial to a fresh pitch of healthy liquid yeast, he'd have a lot more to say than what is written in that simple quote you posted.

There're also two methods of making starters: proofing starters and growing starters. Proofing starters--under the right conditions--won't hurt the overall yeast population if the yeast it pitched when active (just prior to, at or just past high krausen). But if you are growing yeast the starter size matters and it can leave the over-all cell population less healthy than they were before they were pitched if the volume of the starter was too small.

There's too much going on with yeast to paint a black and white portrait--obviously a small starter that is fed with constant aeration lives by different rules than a simple starter that was only given a good shake before the yeast was pitched. So I guess what I am saying is it isn't a one size fits all package. For me personally--I almost never make starters any longer. I start out with enough healthy yeast in a low SG beer, aerate well if necessary, pitch that yeast and use harvested slurry to brew anything afterward.