Manual vs Boundary

I’m confused about boundary vs manual. In podcast episodes 11 (the manual) & 12 (boundaries), Brooke explains that manuals are things that we want the other person to change about themselves so that we can feel better, whereas a boundary is created to protect ourselves from someone invading our personal or emotional space (with a boundary we set a consequence which is an action that WE take, we are not trying to change the other person, and we should be prepared to lose the relationship with them if they continue to cross the boundary). But at the end of episode 12 she describes creating a boundary with her friend who is often late for lunch (Brooke will wait only 15 minutes and then leave if the friend is later than 15 minutes) in order to avoid feeling upset and resentful towards her friend.

This sounds like a manual issue to me (make a request and then have a negative thought/feeling when the other person does not comply), the friend being late is not crossing into Brooke’s space. Rather than setting a boundary, would it be more appropriate for Brooke to let her friend know her preference but then not make a negative meaning out of it when the friend continues to turn up late? This example blurs the concepts for me, can you explain to me please how this is a boundary and not a manual issue?

I have tended to have manuals for my husband because I too want to avoid feeling resentment, anger, frustration, etc and I am working on dropping those manuals and feeling my feelings instead, but is it an option instead to set up tons of boundaries so I can avoid feeling those things (as Brooke did with her friend to avoid feeling upset and resentful)? An example in my life is that my husband often makes plans to take me out to dinner but then things come up at the last minute and he cancels our plans. This makes me feel resentful, so I have decided to set up a boundary – when he asks me to dinner I will say “maybe” rather than “yes” so that I won’t feel disappointed and resentful when he cancels. But now i’m wondering if this is appropriate, it is similar to the example of Brooke and her lunch friend, he’s not crossing a physical boundary with me, i’m not going to give up the relationship if he keeps doing it, so it feels like more of a manual rather than a boundary issue. Should I instead work on my thoughts and feelings of resentment (drop my manual) rather than put up more boundaries between us?