I suspect these are more likely people that removed digikam and forgot about it. Anyone that has what they think is OM Lx 4.1 installed and it did not have digikam installed by default could have a corrupted install or corrupted download, or worse. They should re-download, check checksums, and re-install after verifying the checksums are correct. (If it is my computer I darn sure am doing this a system missing a default package could have other, bigger problems.)
As a tester I do lots (like 100’s) of installs from OM ISO’s and I have never seen a system installed that was missing a package in the package list for that ISO. I strongly suspect that the Calamares installer would instead issue an error message if this happened. Perhaps @abucodonosor could enlighten us on this. I’ll ask on IRC.