well if you want to be more specific, no one in the game is invincible ever.
everyone is just invulnerable to some extent. since everyone can lose a round which is more what invincible means… but i get what you meant and yeah basically. he isnt much vulnerable in shippu
ryu’s ex srk is fully invulnerable through startup into the start of the move hitting. ken is never actually invulnerable during shippu. just the move has a massive hitbox and his hurtbox is very far away from it making it almost have invulnerability. however if ryu did ex srk as ken did shippu, as long as ryu is up close to ken ryu should win afaik.