The plat form immediately next to you you shouldn't be able to reach, but there are two or three to further to the right that you can.
If you can't reach those, then you've found an unintentional bug somewhere :p
It's not the first time that some physics in an unity webgl build are not working correctly on my gaming pc. however on my laptop i could jump much higher. maybe you could contact https://itch.io/profile/snapplers . I had a simmilar problem with his game https://itch.io/jam/wowie-jam-2/rate/552266 but he said, that he may found the issue. could be the same reason?