I decided to look into this. The answer seems to be maybe there is a bit more sugar, but it's probably more likely they taste sweeter because they're bred to be less bitter/sour rather than increasing their sugar content, which is quite hard to do. Go to the link to James Wong's Twitter post near the end of the article to get his (above) take.

https://www.acsh.org/news/2019/08/26/fruit-much-higher-sugar-it-used-be-14243#:~:text=And%2C%20yup%2C%20the%20%E2%80%9Cmodern,been%20a%2054%25%20sugar%20increase.