The whole question of using probability here is philosophically fraught. If you are saying "this has a probability of 50%" then you're saying "this will happen half of the time if you repeat the test". I don't think Harris would win 5 times if you ran that election 10 more times. From that regard, the 50% guess is quite inaccurate, and does just seem to be the pollsters "giving up" in the sense that they're pretty clueless and so ended up going with an even split. This is speculation on my part, but I think that election was decided in Trump's favor pretty decisively long before the publishing date of the last 50/50 poll.
Edit: to elucidate, suppose it rains on 50% of days. One forecaster gives a 50% chance of rain every day. Another gives a 90% chance of rain/not rain and is "wrong" 10% of of time. Both stations are giving you accurate information from a probability perspective (when station A says a 50% chance, you know there's a 50% chance of rain tomorrow, when station B says 90%, you know there's a 90% chance of rain tomorrow) but the 50% chance station is less useful as the number is lower. They have effectively given up in the same way pollsters have given up; they're saying there is no information that could give them a higher probability. The reason a single event can have many different probabilities is because probability is about repeated events. Both stations are predictions accurately reflect the distribution of rain/not rain days.
Edit: to elucidate, suppose it rains on 50% of days. One forecaster gives a 50% chance of rain every day. Another gives a 90% chance of rain/not rain and is "wrong" 10% of of time. Both stations are giving you accurate information from a probability perspective (when station A says a 50% chance, you know there's a 50% chance of rain tomorrow, when station B says 90%, you know there's a 90% chance of rain tomorrow) but the 50% chance station is less useful as the number is lower. They have effectively given up in the same way pollsters have given up; they're saying there is no information that could give them a higher probability. The reason a single event can have many different probabilities is because probability is about repeated events. Both stations are predictions accurately reflect the distribution of rain/not rain days.