Granted there was a great deal of propaganda—especially the "7 Arab armies promptly invaded!" line; further, there is no direct evidence of the alleged "Arab broadcasts" urging Palestinians to flee to await slaughter of the Zionists.

Yet there are several points here that are misleading:

Longstanding negotiations with Emir/King Abdullah had broken down—the king urged the Yishuv accept dominion status in an enlarged Transjordan, unacceptable to the Yishuv—by 15 May '48 there was no agreement between Transjordan & Israel.

Arab guerillas & irregulars under the command Hassan Salameh & Abd el Kadar attacked Jewish/Israeli positions using hit & run tactics (which the Jews reciprocated). Although exiled in Lebanon, the most avowedly antisemitic of Palestinian leaders, Amin al-Husseini, still influenced Palestinian strategy (Abd el Kadar was his cousin).

In short, first the Yishuv, then Israel couldn't gamble on the Arab's ultimate strategy, or the possibility of their goal being to protect the Palestinian portion.

That being said, Ben-Gurion refused several efforts by the US, Great Britain & the UN to broker truces out of a desire to gain more land.