The post you are reporting:
You are right, a State (as opposed to occupational) pension is paid by the country where the majority of your pension contribution has been paid in.
However, healthcare is provided via reciprocal arrangements deriving from that state pension payment. So, for a UK State pensioner in France, healthcare is provided because the citizen completes what is called an "S1" form. In short, that form reads "Dear UK, do you accept responsibility for this person?" The UK replies, "Yes, we do, please provide healthcare to them and we will cover the bill". That process simply would not happen if we were not part of the EU and EU Coordination Regulations; the pensioner would have to fund their own healthcare (regardless of ability to pay - you take the point).
Spain is entirely different. There is a real problem and I kid you not, the Spanish press receives lots of letters to the editor along the line of "All of these Brits, coming here, using our public services.." in just the same was as we tend to do with Eastern Europeans. Only five years ago the Valencia authorities become so overwhelmed with Brits accessing their health system that they had to appeal to central Government for help. The point I make here is simply that EU membership is a two way street and we only ever get to hear about the single direction of travel.
Apologies if this is fairly boring! All I am really trying to do is to add, where I can, factual accuracy to the debate. It dismays me that we are being asked to take such a fundamentally profound decision based on such little and at times, entirely inaccurate information.