Smyslov fan really is stretching the limits of credulity with a number of things he's saying without technically being "wrong". I can believe inventing an opening system, or a "technique", but it's hard to image some brand new "never seen before" tactical sequence.
In the old books of Tarrasch and Nimzowitsch, they used the word "amateur" as an insult to chess ability all the time. That's practically what the word meant, rather than anything about making money from chess.
When you get totally absorbed in a game to the exclusion of nearly all else, that's pretty much the same as being professional. Most of these old players didn't have a difficult life, they had some inheritance or some other way to live an easy life.
Schlechter did amazing against Lasker (though he didn't beat Lasker how close the match was tells me that Schlechter would steamroll Adolf Anderssen.)
Lasker was incredible when he won New York 1924 ahead of Capablanca and even Alekhine.