I will be more than glad to assist you with your concern.
Before I can continue, could you please provide me the document or link where you are seeing this information?
And if it is possibles screenshots where you can see this concept?
As soon as you reply I will provide you further assistance.
Hope I can hear from you soon.
In regard to your concern, on the first link, you have provided (http://intelvintage.info/intelmcs.htm) MCS stands for Intel Microprocessor System.
On the second link (https://en.wikichip.org/wiki/intel/mcs-4), MCS stand for Micro-Computer Set.
Both terms, are synonyms if there are referred to chips, as per the articles that you have sent.
Please do not hesitate to confirm if there is anything else that I can help you with.
I would like to know if the information provided to you was able to solve your concern?
In case if you need further assistance do not hesitate to reply back.
I am looking forward to hearing from you.