Think about the alternatives - either you divide the stack into separate teams or you have non-overlapping experts in the same team. Both are horribly worse.

With the multi-team architecture, no one can deliver anything on their own. They all have to hand off their work to someone else and receive handoffs from someone else. Rework becomes huge as downstream teams with expertise not present upstream identify flaws and send work product back for revision.

With non-overlapping experts, you have a team of N with N bus factors of 1. No one can get sick or take vacation. If someone quits, dies, or wins the lottery, the whole team shuts down while they try to find a replacement. You can fix this by hiring 2 or even 3 experts per area. So now your team is full of redundant experts that fight for expert recognition. The handoff problem remains but is somewhat lessened.

A full-stack team is not a team of pure generalists. A full stack team is a cross-functional team that owns the entire value stream (design to production) and cross-trains internally. Hiring people with specialized knowledge is predicated on their willingness to learn all other areas and teach their area. Only T-shaped professionals (depth in one area, breadth across the stack) inhabit the team and only people with the humility to learn need apply.

Over time, a full stack team outperforms every other team. The team is internally redundant on all tech, so bus factors are lowest when new people are added and bus factors continuously get larger over time as people cross-train. New hires have built in training because the team is always training. New tech can be added regularly because everyone is always training and learning.

Full stack teams are the best form of software team hands down.