Boundary crossings can be a warning sign, especially if there are a lot of them, but there are times when they are useful and appropriate too. The key there is who's purposes are served by allowing the boundary crossing. What motivates it? What is appropriate for one person isn't necessarily for another. To give a client a flower because it is meaningful for the client to be remembered that way is different than to give a client a flower in hopes of influencing how the client feels toward the therapist, especially if the therapist wants something from the client. Meeting outside of the office might be the only way that a client can start receiving treatment if that client is fearful of being alone in an office with a therapist, so going for a walk or meeting in a public place might be helpful to that client. That's different from the therapist who says "I have had a lovely time with you, how would you like to go somewhere with me and spend more time together?" Who's interests are really served? It should always be the client's.

There are therapists with too rigid boundaries too, IMO. Some are so afraid that they will get in trouble, that they will never give a hug, accept a gift, talk to a client outside of the office, or tell anything about themselves. They are still serving their own purposes (avoiding risk) more than the client's (for some clients, all of those things might be needed and appropriate). A good therapist maintains clear and appropriate boundaries, but still considers the best interests of the client first and foremost. They can be flexible when that is what a client needs, without doing or allowing anything inappropriate.