If you committed an act that is considered sinful, but the circumstances were such that it would mitigate the seriousness, it may be justified for the priest to probe a little. Such a case may be that you robbed a store, but the real criminals told you if you don’t rob the store for me, I’ll kill your mother. Or you acted immorally, but you were drunk when it happened. The priest should know this because it would effect the seriousness of the immoral act, and you may have also been able to prevent it or prevent it in the future becasue he should councel you on avoiding places or occasions of sin.
The other problem which we face today when one goes to confession to a priest who is holds to the traditional moral teachings of the Church, and as the OP suggests a parish where the EF is either habitually or exclusivly offered is that the priest if he does not know you, cannot be sure that you were properly instructed on Catholic moral teachings, or preparation for confession. The confessional is also a place where we can be taught about the Faith. So bringing up these other sins can be his way of instructing you and enlightening you about sin, so you can be aware of it and hopefully avoid it in the future.
If you are very fortunate, you may just have a priest with the charisms of St. Padre Pio or St. John Vianney. I fear and hope to confess to one of those priests.
Sometimes things that are good for us are not easy. Exercise, spiritual or physical can be painful at times, but in the case of spiritual exercise, the rewards are heavenly.