Do you give truma from cherries?

Rav Elazar Menachem Shach and Rav Isaac Zev Soloveitchik seem to be having an argument about the Rambam in Laws of Truma ch 1 halacha 5.
[That Soloveitchik was the son of Reb Chaim. I think he is the one who founded the Yeshivat Brisk in Jerusalem.]

I have mentioned before today some of the main points in this subject and I might try to go over them again. But right now I wanted just to focus on this argument. I am not sure how to organize this also so bear with me.
The basic Gemara from where this all starts is in Yevamot 16 side a. עמון ומואב מעשרים מעשר עני בשביעית. (Amon and Moav give tithes to the poor on the seventh year.) And down a few lines is says דאמר מר הרבה כרכים כבשו עולי מצרים ולא עולי בבל דקדושה ראשונה קדשה לשעתה ולא לעתיד לבא והניחום כדי שיסמכו עליהם עניים בשביעית (for the master said many cities were conquered by the Jews coming out of Egypt but were not settled by the exiles returning from Babylonia because the First sanctification sanctified the land only for the time when Jews would be living there, but the second sanctification sanctified the land permanently, and they left those cities in order that the poor would have access to the tithes for the poor on the seventh year.)

Rashi is perfectly clear. The areas of עולי מצרים are not sanctified at all and there is simply a rabbinical decree to give the tithes to the poor and לקט שכחה ופאה. No Truma or any other maasar.

The Rambam writes this same thing as the Gemara but adds a few words. הרבה כרכים כבשו עולי מצרים ולא עולי בבל דקדושה ראשונה קדשה לשעתה ולא לעתיד לבא והניחום כשהיו ולא פטרום מן התרומה ומעשרות כדי שיסמכו עליהם עניים בשביעית

"They did not פטר (absolve) them." There is only one way to understand these words as far as I can see. That those areas were obligated and when people returned from the exile in Babylonia they left them in their original state of obligation. And that is exactly how Rav Shach understands this Rambam [I think.] That that land is obligated in Truma and Maasar from the Torah and the whole idea of קדושה ראשונה קדשה לשעתה ולא לעתיד ךבא is relevant only to sheviit.

That is as far as I can get right now.

Let me just add that Rav Soloveitchik holds that the land conquered by Jews coming out of Egypt but left by the exiles returning from Babylonia has all the regular laws of the land of Israel according to the Rambam. This is from what I can see what Rav Shach is about to disagree with. To me it seems at this minute that he is going to say that it has all the laws of the land of Israel only in reference to the laws of truma and maasar but not sheviit.

You can see already where all this is going. Rav Shach is probably going to be saying that those lands were not obligated in Sheviit--but the Chazal [sages] could have made those lands obligated in shevviit if they had wanted to. But they decided not to, and so the only obligation they have is truma and maasar. That explains the language of the Rambam here. And I am guessing that even without reading further that this will end up explains a good many of the other questions that this subject has in it.
I mean what is the most obvious question here. It is the fact that the Rambam holds קדושה ראשונה לא קדשה לעתיד לבא  and yet still holds from  כזיב until Amon is נאכל אינו נעבד and he explains in that very halacha that נאכל  refers to the ספיחים which means he hold the land has the holiness of  שביעית. So that would probably mean it has a law of Sheviit by decree of the Sages until the people of Israel return a third time at which time the full holiness of teh Torah will apply.