R' Chaim's chiddush re: al ha'nissim said alongside yaaleh v'yavo instead of in its proper place

The Pninei Halacha from the Mir Yeshiva quotes the following shayla that R' Moshe Shapira heard the GRI"Z quote b'shem R' Chaim: someone in their davening on Rosh Chodesh Teives accidentally said al ha'nissim alongside yaa'eh v'yavo before v'techezena eineinu... and wanted to know whether they have to repeat shmoneh esrei or not.  R' Chaim told the person to ask his FIL R' Raphael Shapira, and to mention that he holds that yaaleh v'yavo is in place of retzei.  

R' Raphael Shapira paskened that since the person said yaaleh v'yavo first and then al ha'nissim, he has to repeat.  Had it been the other way around, he would be yotzei.

The whole thing sounds like a riddle.  The shayla was whether al ha'nissim is a hefsek, but R' Chaim's response was about yaaleh v'yavo being part of the bracha of retzei.  Somehow that led R Raphael Shapira to say it depends on what was said first, with no further explanation.

What's going on?

Here is the mehaleich that they put together to unravel the conundrum:

Since al ha'nissim is not part of the bracha of retzei, it would seem to be a hefsek (see O.C. 108).  

As a result of the hefsek, it is as if the beginning of the bracha is cut off from the end.  

If in theory the end of the bracha could stand on its own, then this would be like an interruption in between two brachos, which b'dieved does not negate the entire shmoneh esrei.  

However, since v'techezena... onward does not reflect the theme of avodah or korbanos, which is the essence of the bracha, it therefore cannot stand on its own -- it's an end with no beginning.  The entire shmoneh esrei is therefore lost.

What R' Chaim was mechadesh to his FIL was that in the case where you say yaaleh v'yavo, things are different. See Rashi (Shabbos 24a) who writes אומר מעין המאורע בעבודה. לבקש רחמים על ישראל ועל ירושלים להשיב עבודה למקומה לעשות קרבנות היום:  Yaaleh v'yavo does reflect the essence of the bracha.  So long as you can attach it to v'techenza... onward, you have a complete bracha.  

Therefore, concluded R' Raphael Shapira, if al ha'nissim was recited first, you are left with yaaleh v'yavo + v'techezena... and have a complete bracha and are yotzei.  If, however, yaaleh v'yavo was recited first and then al ha'nissim, it creates a break in the middle of a bracha, in which case the bracha is lost and shmoneh esrei must be repeated.