I don't think I've ever mentioned this, but I really enjoy reading your posts. Thank you for sharing these. I'm a big fan of Clyde E. Love's book on squeezes, so forgive me for using his terminology.
Your belief is false. There are many different types of squeezes, some of which operate against any distribution, and some of which only operate against specific distributions (kind of like a finesse). Thankfully the hand you show is of the "simple/basic squeeze" type (the name of which should be taken with a grain of salt, in that basic/simple is very much a relative term), which is arguably the easiest squeeze of all. If the lead was anything other than a heart it would be of a far more complicated "Type R double squeeze" type, but fortunately(?) that choice was eliminated by the defense.
1 Typically a squeeze of this type is a last resort for an extra trick. In this case your only alternative chances for 13 legitimate tricks are singleton king of clubs or diamonds JT9 tight, which coincidentally are also picked up by the squeeze line. So we immediately go for the squeeze instead.
If the defenders' hands are such that the squeeze produces an extra trick it is said to 'operate'. To squeeze a defender you need to identify
two threats, i.e. cards that might potentially win the last trick for you. If one defender and one defender only can guard these threats, i.e. holds cards strong enough to prevent you from cashing these cards outright, this defender is said to be
busy in two suits. For a squeeze to operate a defender needs to be busy in two suits.
On this hand your threats are the
♣Q (making the defender who holds the
♣K busy in that suit) and
♦8 (making the defender who holds at least 4 diamonds busy in that suit. Note that since you have 6 diamonds between declarer and dummy it is impossible for both defenders to hold 4 diamonds). On your example layout these holdings lie in opposite hands, and so there is no squeeze. If they were held in the same hand the defender would be squeezed (in this case regardless of if it is West or East).
The best line of play is in the spoiler below, but I recommend you rearrange the defenders' hands and try again first before checking.
1AL78 points out the double squeeze chances, but on the heart lead there is no late entry to the
♥2 threat so it does not operate.