You were in the 2BR portion of a 3BR unit, which is actually 2 units behind the outside door. The 3BR units are all at the ends of each hall. The layout is indeed different from the dedicated 2BR and 1 BR units. If you want a connecting door, you have to leave the 2 doors open and use the outside door as the entry door. It is as secure as the entry door of any more typical units.
Interesting that there are no adjoining doors between the 1BR and 2BR. Grande Vista 3BR has similar setup in the 3BR's which there is an door that opens into a foyer and separate key card entrances to the studio and 2BR side but there is still an door inside that you can open between the 2BR and studio. This way, you do not need to leave the 2 doors open.