PM sent regarding my .22 pistol you might be interested in

The glock deminoshed capacity magazines (the CA 10rounders) are very tight and very difficult to load rds 9 and 10 into the magazine. There are also many firearms that when a mag is loaded to full capacity and inserted into a closed slide firearm are very difficult and must be slammed in and can also put tension on the slide making it harder to rack. This is normal and can change slightly from magazine to magazine and solved by loading from an open slide as well as loading a round short as you have discovered.
On the other hand there are many firearms that the magazines are easier to load to capacity and have less effect on how hard the mag is to seat on a closed slide as well as how hard it is to rack the slide on a full mag.
Neither is correct or incorrect or better or worse and this is generally caused all by how tight the mag spring is and the gun is designed.

There is the obvious advantage of some ease of operation with different designs though weaker type mag springs are not always better as a high mag spring tension can help in reliability of both round ejection and next round feed ability. Too loose as well as too tight can both cause issues.

As simple as a magazine seems they can actually be very difficult to get "right" and themselves be responsible for poor performance of a firearm. One of the biggest example of this included the US military with the implementation of the modern m4/m16 a3/a4 pattern rifle were 60 to as much as 70 percent of failures in function of the firearm were attributed to old worn out or just poor quality production magazines.