Not necessarily. It implies that captain america has strategies to defeat opponents that are physically stronger than he is, since he regularly spars with dudes that can bench press battleships.
Thor would kill him in a serious fight, but Cap has beaten enough people in the 20, 30, 40, and 50+ ton range (see the list I i made a few posts up) using a combination of raw strength and skill that just about anyone who isn't throwing moons like baseballs is going to have a hard time.
This isn't even THAT uncommon. Spiderman is in the 10-20 ton range, and regularly takes out opponents WAY stronger than he is, again using his skill and speed to gain an advantage. You can even look at guys who have no powers at all but INSANE levels of skill like iron fist, shang chi, or taskmaster easily taking out opponents with superhuman strength.
Comics, bro- that's how they work. Techique, speed, pressure points, superior tactics can give you the W and let you punch above your weight class.