Short actions concentrate more recoil force in the stock. So even if the short action is stiffer, you could end up having more muzzle rise because the stock material is deflecting more. Or worse, the stock material yields and the bedding fails. Kelbly for some time made a longer action with recessed barrel threads (for the life of me I can't think of the name - help, DanH) that solved this perceived problem. On the other hand, BR rifles have also been made with Wichita pistol actions, which are extremely short. So it seems you can make any action length work. Long and short both have advantages and disadvantages. Not something to worry about, other than maybe a glue-in without a recoil lug in a strong recoiling caliber.
JMHO,
Keith