This long account, or series of incidents, involving Rabban Gamliel and, particularly, his disputes with R' Yehoshua is fascinating in many ways.
One involves the editing of Sefer HaAggada. In the middle of this account, the text mentions the liberalization of Rabban Gamliel's rule that scholars would not be allowed to enter the bet midrash unless their internal character was consistent with their outward appearance. Then the account mentions a dream that Rabban Gamliel had. Our text says, roughly, as follows: "Rabban Gamliel had second thoughts. He said, 'Perhaps, God forbid, I have withheld Torah from Israel. [At this point, the Hebrew text has an ellipsis, though there is no break in the text as it appears in b. Brachot 28a.] They showed him in a dream white jugs filled with ashes." In Sefer HaAggada, there's an ellipsis here, and the text then moves on to another incident.
The image of white jugs filled with ashes is understood as a metaphor for students whose appealing exterior (white ceramic) was belied by their inside character (gray ash). It seems that Rabban Gamliel is being told that his stringent admissions criteria were justified, and that people being admitted under the new rules really were not appropriate -- he had not withheld Torah from Israel.
The problem is that, what follows in the Gemara, where the Sefer HaAggada has an ellipsis, is the following: "No, that's not the case; it was just to settle his mind that they showed him this." (Soncino: "This, however, really meant nothing; he was only shown this to appease him.") It seems that the Gemara's conclusion is that Rabban Gamliel was unjustified, and the liberalization was proper. Bialik and Ravnitsky could easily have included this extra line in their text; why did they omit it?