This is an oddity rather than a bug. The option list for the saluationName field is originally taken from Global.json in en_US and not from the user's language. This is correct because a salutation is a salutation and there is no translation - Mr. is English and Hr. is German but they stay as they are so no need to translate (a Mr. doesn't become Hr. just because the user uses German).
Unfortunately a change in any of the 4 entities concerned (user, lead, contact, target) creates an entitydefs and a json file with the new options only for one module in one language. So adding a 'Sr' in contact for Spanish then is shown in Spanish and for contacts only.
In this particular case (I can't think of any other standard fields) it would be better to create a en_US Global.json in custom in order to be consistent.
Unfortunately a change in any of the 4 entities concerned (user, lead, contact, target) creates an entitydefs and a json file with the new options only for one module in one language. So adding a 'Sr' in contact for Spanish then is shown in Spanish and for contacts only.
In this particular case (I can't think of any other standard fields) it would be better to create a en_US Global.json in custom in order to be consistent.