Matchplay 4bbb - ball hits ball on putting green

Just confusing it with strokeplay rules, I would guess. I did it myself a couple of years ago, picked my ball up before realising I still had a putt for a half. I've been playing for 65 years & I'm sure that the rule has been the same all that time.

In terms of experience playing, I'm a couple years short of your 65, but agree that it's been that way for match play for a long while. Actually, I believe that, in match play, the player could insist that the opponent's ball not be marked and lifted, that the player "controlled" the opponents ball, but I don't have the evidence to support that. Edit: see below,
The Stymie
A stymie was possible only in matches involving one ball per side. On the putting green, if two players' balls were more than six inches apart, there was no provision for the ball nearer the hole to be lifted. If that ball lay directly in the way to the hole of the ball to be played then the player was 'stymied.'
He could try to play around or over the interfering ball, but if the nearer ball was struck, no penalty ensued. However, the opponent had the option of playing the ball as it lay or replacing it. If the nearer ball had been knocked into the hole the opponent was considered to have holed out with his previous stroke.
The stymie was really born by default. In the original rules of 1744 only when balls were touching could one be lifted.
This was adjusted by the Gentlemen Golfers Of Leith in 1775 to touching or within 6 inches of each other.
1789 Gentlemen Golfers introduced this rule: 'In all time coming, in case in playing over the links any ball shall lye in the way of his opponent's the distance of six inches upon the hole green, it shall be in the power of the party playing to cause his opponent to move said ball'.
1812: St Andrews re-worded the rule slightly, but the principle of the stymie remained: 'When the balls lie within six inches of one another, the ball nearest the hole must be lifted till the other is played, but on the putting green it shall not be lifted, although within six inches, unless it lie directly between the other and the hole'.
1830 Montrose code specified that the rule did not apply to stroke play or four-balls.
Sept 1833 St Andrews Golfers voted to abolish it, but it was reinstated the following year (by the now R&A) as 'When the balls lie within six inches of each other in any situation the ball nearest the hole to be lifted until the other is played'.
The word stymie only appeared in the rules rarely: Musselburgh 1834, 1851 and 1858 R&A, applied to all stroke play. The USGA used the term in notes to Rule 31 in 1938 and 1947. However, all the rules books of the 20th century, up to its abolition, used 'Stymie' in the index.
1891 R&A rules vaguely tried to remove the stymie from stroke play, stating that the ball may be lifted by the owner if he felt that it may be of advantage to the other player, or 'throughout the green' a player could have any ball lifted which might interfere with his stroke - but 'throughout the green' was not defined.
1899 Stroke Rule 11 and Medal Rule 9 stated the same thing.
The wording was made much clearer in 1902.
1920 USGA had a one-year trial of allowing the stymied player to concede his opponent's next putt.
1938 USGA introduced a modified stymie rule, initially for a trial period of two years, allowing a ball within 6 ins of the hole to be lifted if it was interfering, regardless of distance between balls. The rule was subsequently made permanent from 1941.
1950 abolished by USGA completely, but the organisations affiliated to the R&A were not inclined to do away with it.
Finally abolished worldwide in the joint rules of 1952. Now, lifting on the putting green was at option of owner or opponent if it was felt that the ball would interfere or be of assistance.
1956 In match play, the rule was changed such that the ball nearer the hole could only be lifted at the request of the player about to play. In effect, the player about to play had 'control' over his opponent's ball.
From 1984, a ball may be lifted if it may interfere with or assist another player in all forms of play.
A small echo of the stymie can still be found in the Rules - on the putting green if a player's putt strikes an opponent's ball, there is no penalty in match play but it's a two-stroke penalty in stroke play.