Either. Both. Neither. It depends on a lot of things.
The split you use is influenced by your actual goal, your needs/weaknesses/priorities, your actual practical schedule, etc.
Push-pull-legs is pretty versatile. Paul Carter had an article all about it that laid out how it can be used to train each bodypart once a week (3 total workouts per week) or hit everything three times a week (6 workouts per week). That versatility is pretty useful for programming.
The Arnold split you wrote, from the Encyclopedia, is designed to be run 6 days a week hitting each bodypart twice. Again, Paul Carter wrote about how to plan an “Arnold split” with a back/chest day, leg day, back/shoulders day, and arm day each once a week.
Then program it smarter. Of course the shoulders are getting hit during pressing (and some rowing) movements, but getting “too fatigued” means you’re hitting them directly with too much volume and/or too much intensity.
In a push workout where you’ve presumably already done one or two types of chest pressing (benching and dips, for example) you might only hit shoulders with laterals and no shoulder pressing.