He withheld the sacrament - not the grace of the sacrament. The grace of the sacrament was inaccessible to the sinner whether he received the Eucharist or was denied it.
a leading German RC historian, Ignaz von Dollinger
(1) Dollinger is not a Roman Catholic historian. He was an apostate historian.
(2) Dollinger's work was done over a century ago. Many documents have been found and much research has been done since his day to show that his conclusions are often incorrect.
(3) As an apostate he is a biased witness. A strong opponent of auricular confession is not likely to produce historical evidence in support of it.
(4) There is a difference between private auricular confession between a penitent and a priest and the truly sacramental aspect: that is, absolution. Public rites of penance for sin and pronunciations of formal absolution are attested by the earliest Church Fathers in both the East and West. Even today in the Catholic Church public rites of absolution may take the place of private confession in certain circumstances.
(5) Auricular confession as it is practiced often today (i.e. - anonymously, often in a darkened booth to shade the face of the penitent) is older than Dollinger ever suspected. It is attested in 8th century Ireland, for example - and Ireland on the outskirts of the Empire was rarely the first in anything related to sacramental ritual.
(6) Auricular, but not anonymous, confession has been practiced for centuries in the East - the Eastern Churches formally recognized it as a sacrament centuries before Dollinger was born.