I work out of my house, but I do have to be out of the house for up to 5 hours from time to time. I also think it is wrong NOT to teach tour dog to be comfortable by themselves. Sooner or later, they all have to deal with it for some reason or another. It can be quite stressful if they have not learned.
While separation anxiety is a real "thing", and can happen with a dog of any breed, I do NOT believe that Havanese are more prone to it than any other companion breed. REAL spearation anxiety is a serious disorder, that often requires the help of a trained behaviorist, and sometime medication to deal with. What I see and hear about most in Havanese is dogs where the owner has not taught them to be on their own at all, and then are TOTALLY surprised that the dog gets so upset when they do need to leave them.
I have three Havanese, from two different breeders. NONE of them have a problem staying alone. But I have to say, we have worked on that. And it is VERY hard, when you have multiples, to make sure that they ALL have turns staying home alone, and, likewise, all have turns going out in public with us alone. We used no "special protocol" to avoid SA. We just were cognizant of the need to train independence, just as you need to train your puppy in so many other ways.
We don't ROUTINELY leave our dogs alone for more than 4-5 hours. In fact, even that isn't really "routine", as it happens periodically. When we know ahead of time that we won't be home all day, we arrange for someone to come in and play with them and let them potty, like Shama. However, when my husband had a major heart attack and was hospitalized for 10 days, Kodi (he was an "only dog" at the time) did fine left home alone gated in my office with water, some chews and his litter box for 10 hours a day. Did he enjoy it? I doubt it. But we weren't exactly enjoying ourselves either... we were in crisis mode!
He survived with no ill effects, and while he sure was happy to see me when I got home each day, he didn't seem particularly stressed.