Now that I've made you angry. Here's what I actually mean.
Even the best product thinking engineer should not be placed in the position to be both a product manager AND an engineer on the same product/project.
Product management is often about saying NO. It's about long term, big picture thinking. It's about the what, when and IF something should be done. It's about stakeholder discussions, consensus building, visual design, marketing, customers, business considerations and more. It's about picking which hill to take, bringing the right team together and motivating them to get it done (to use a military metaphor).
Engineering, on the other hand, is mostly about saying YES. It's about getting the job done. Solving problems. Figuring out HOW something WILL be done. It's about being deep in the details of the code and trying to find your 'zone' to make magic (a zone that is easily interrupted by meetings!). It's about being the person the product manager can depend on to actually run up the hill and plant the flag while they're off picking the next battle field (to continue the military metaphor).
These are totally different head-spaces and roles. Often they work well together. Sometimes there's a healthy tension with one side pushing the other to "do more" or "get more focused" or "be more specific" etc (in both directions).
Someone with an engineering background might actually be an excellent product manager when placed in that role (and they often are!) but asking ANYONE to do both roles is often asking too much.