I read much about “ad orientem” that I find difficult to comprehend. But I also read many falsehoods, as if ad orientem was the only posture before Vatican II. Nothing can be further from the truth.
I have an old 1935 Ceremonial that indicates the different possible configurations of a church.
A church without a choir would likely have the altar at the far end of the sanctuary up against the wall. In that configuration ad absidum was the only possible way to celebrate.
Churches with a choir though, such as a cathedral with a chapter of canons or an abbey’s conventual chapel, could have:
Altar at the far back of the sanctuary against the wall; celebration would be towards the apse for everyone.
Altar between the nave and the choir, turned towards the choir. Celebration would be ad absidum for those in the choir, and versus populum for those in the nave.
Altar between the nave and the choir, turned towards the nave. Celebration ad absidum for the faithful in the nave, but versus populum for those in the choir.
Moreover in many of these places, even before the Council, the tabernacle could be in a side chapel. This was often the case in Benedictine abbeys. These indicate that whatever symbolism the fans of “ad orientem” celebration seem to think exists, wasn’t consistently applicable for all participants in the Mass, being ad orientem for the clergy or religious here, and ad orientem for the faithful there. So what is the symbolism in that? There isn’t any that I can discern.
We mustn’t confuse nostalgia for what happened in the local parish church with being the truth everywhere. Nor should we confuse entrenched customs as written in stone and immutable. According to the Catholic Encyclopedia from an article written in 1910:
When the custom of erecting the episcopal throne on the gospel side of the sanctuary became prevalent, the high altar was removed nearer to the wall of the apse. The object of this was that sufficient space might be allowed between the lowest step of the altar and the communion-rail (six to twelve feet) for the proper carrying out of the ceremonial, and for the accommodation of the clergy who frequently assisted in large numbers at the solemn celebration of Mass and of the Divine Offices.
Prior to that, the cathedra was at the apse and the altar in the middle of the sanctuary. It seems to me then that the reason for an altar configuration that obliges celebration towards the apse was entirely practical, and not symbolic.
The only thing that the picture conveys to me is that the altar in that particular church is configured in such a way that ad absidem is the only reasonable option to celebrate Mass. Indeed the picture shows that it is an altar against a wall, and thus there is no opportunity for the priest to celebrate in the other direction, assuming there isn’t another free standing altar behind the priest.