Welcome to tfl!
There is below spec, and there is too short causing a problem. Max length spec is .898" Trim to length is a suggestion (NOT a requirement) and depending who's making the suggestion its usually either 0.010 or 0.005" below listed max. the idea is to trim it enough that it won't stretch enough to be over max and require trimming every time.
With the .45acp, this is not an issue. Cases are shorter than max spec and nearly always stay that way.
Go get a box of factory .45acp from a quality maker and measure the unfired case, I'll bet you a cookie its LESS than .898"
Now, the spec is for the .45acp to headspace on the case mouth, so one thinks case length is critical, and it is, if too long (very, very rare) but due to the construction of most semi autos, its not that critical if its a bit too short.
As was mentioned, with nearly all semis, too short a case will be held in place by the extractor and fire just fine. Just as too short a case fired using a moon clip in a DA revolver will be held in place by the clip, not the mouth of the case in the chamber. HOWEVER this changes when firing the .45acp from a single action revolver, such as a Ruger Blackhawk. In that gun there is a possibility that too short a case could allow a misfire.
I've never bothered keeping track of .45acp case lengths (other than seeing they're all under max length) and I've been shooting autos since the 70s and a Ruger Blackhawk in ACP since 1983.
Literally, unless you are having a problem, there is no problem with cases under trim to length.
I'm think if you had cases as short as .800 they'd still work in a 1911 (feeding from the magazine) not so sure they would be ok in a Ruger Black hawk. In my Webley Mk V, using clips, as long as they're long enough to hold the bullet, they work.
Hope this helps.