Appeals Committee. Disputed situations in tournaments.

It is obvious that when you use the scouting ability, you already see where the opponent's heroes are, so this contradicts the statement that "you don't see where the blue hero is," meaning that by attacking with a reinforcement, you are violating the rules.

The rules are the same for both blue and red. If an exception is made for portals, it means that blue should not rely on a red rush and leave a hero in the portal, assuming that red can (should) see him using the scouting ability. In other words, if you want red not to attack with a reinforcement on the first day, leave the portal. Again, there is a caveat in the rules regarding the impact of reinforcements on the outcome of the battle, and red has the opportunity to assess this impact on his turn by viewing the size of the blue army using a spell and may decide to remove the reinforcement that will prevent him from winning without violating the rules about the red rush, which is impossible to do while on the other side of the portal. That is, as Dirty writes, you really need to physically see the blue hero, then the red rush is possible.