The size of the testes does not reflect if a men has recently had sex or not. The size or state of position they are in, ie. compressed and small or dangling and big, do reflect, however, sexual arousal, room temperature, and climate comfortability.
When not sexually aroused, the scrotum is usually larger and free to dangle, as to help in the production of semen and keep the temperature slightly below body temperature.
When sexually aroused, the scrotum compresses to prepare the "path way" for the semen to ejaculate with the required force.
Usually when it is cold, the scrotum will also compress to keep a comfortable temperature for the sperm to produce and stay alive, when it is hot the scrotum will drop away from the body more to cool off.
More about heat and coolness. The body likes to keep the testicles as close to a certain temperature because that's optimal for creation of sperm. So if it's cold (or you just got out of the pool) they shrink up into the body to stay warm. If it's hot, they hang down seeking a cooler climate.
There's also an orgasm reflex that causes the testicles to tighten back up toward the body, but that's another thing.
Lol love this question. It may indicate that he has had sex. After I have had orgasm my balls are always smaller because they have been drained of my cum. Also different factors contribute to a man's sperm production. Some guys just have really great ball sacks that are big ad healthy and full of lots of sperm. Other guys have smaller pairs that don't produce as much semen. If his sack is always smaller, it usually means he has been cumming and his balls get smaller when they are drained of his jizz, lol.
Are you talking about the testicles themselves or the sac? The sac is very susceptable to temp changes. The warmer it is the more stretched out it is and the cooler it is it shrinks back into his groin.