It's not bugged, it's obviously for balancing reasons. You can't juice one stat too far without leveling the other. To gain intelligence quickly you need to gain more strength by reading, and to read quicker you need to gain more intelligence by lifting.

If this were a real scenario you would have to be careful not to switch back and forth much or you wouldn't progress until you got new training equipment

You'd go from reading "see spot run" to increase your strength, to later, after exercising having to read textbooks to gain strength.

You would want to max out one stat as far as you can in one go, then switch to the other and do the same.

Shitz literarily unplayable