First, here are a couple points I slightly disagree with:
(Doesn't play by self) "Needing a parent or playmate to play with demonstrates her need for attention." Wow, guess what. Kids do actually need attention-- and lots of it. Kids also have to learn how to play by themselves with our help, and we have to make sure to give them plenty of attention during other times. [Taking Adansmama's comment into consideration: my son is an only and also spends a lot of time by himself. My point is that WE as parents need to teach our kids to play alone; it does not come naturally for some kids who are very connected with their parents. I wasn't suggesting that the kiddo's couldn't, just that they do need to be taught. Many children are inclined to being in constant contact, so we must teach them how to feel comfortable on their own.]
(Unwillingness to share) "Sharing is a difficult concept for lil ones to master, but once a child reaches the age of 4, she should be more willing to share toys, snacks, etc. with friends and siblings." Some kids, esp. onlys or kids who *have* to share a lot, can be challenged by this. I know kids in their 6s and 7s who are still anxious about other kids using their toys. It's not ideal, but they are out there, and it's not usually 'greed' or 'spoiled' I see, but some anxiety.
I want to say here, before going any further, that I really don't like these sorts of surveys and articles. They are often long on the theory of 'what' might be wrong with your kid (or parenting-- and I think this article didn't do any favors in labeling the child 'spoiled, because some of these issues are parent-driven) and short, as you noticed, on any advice. This is part of the problem with the media and parenting in general and contributes, I believe, to the dissent between parents.
Here are some questions I would want to ask:
Are you able to make clear limits with your son regarding the time you spend with him and the time you want to be spending otherwise? Does it feel balanced to you?
Where in your son's day/life/activities do feel you are making above-and-beyond adjustments for him to function smoothly or making compromises to what you feel is reasonable to avoid his getting upset? Those would be areas I would look deeper at, to see what it is you are avoiding. Is it an outburst? What could you, the parents, and the OT come up with to help him adapt/transition to new, more reasonable expectations during those times?
Does he have an allowance, or do you and your husband find yourself buying toys and desired items 'on demand' instead? If 'on demand'-- what does that look like? Are you happy to have made the purchase, or do you make the purchase to solve a problem? If your son doesn't have an allowance, look into how Love and Logic suggests doing it. (our son is five and knows that he has to save up money for most things; we support his art supplies, because this is his favorite endeavor, but we do not buy toys or specials very often-- those are reserved for Christmas/birthdays, etc.)
Do you find yourself working around your son's needs all the time, or do they feel manageable? Do you run the day, or does his day run you? This would be another one to talk with the OT about-- what are reasonable 'needs' for your son (in their opinion) and what do they think might be excessive concessions made on your part? Does the day feel like the needs of the entire family are being met?
I can't say that there's a simple approach because I do not know exactly what your child's particular needs are. Each kid is different. Since you have an OT who knows your family and has worked with your son (and loads of other kids) I might be asking them for advice. (I don't know why your son is seeing an OT, so I'm trying not to assume what, if any, underlying issues there may be. I will say this, however, I really *hate* the word 'spoiled' when used regarding children. It insinuates that they are irreparably damaged, and it's a degrades the parents as well. So many parents are caught out by their child's level of need that they often make concessions to make things go smoothly. That, to me, speaks of the parents who need more support and resources, not more judgment. Unless a parent has some issues (usually mental health ones) where they are expressly grooming their child to be a demanding, controlling little person (and some do, due to their own unaddressed issues)-- then, yes, THAT is spoiling.