In meseches megillah (22A) sefaria translation:
מיתיבי פרשה של ששה פסוקים קורין אותה בשנים ושל חמשה פסוקים ביחיד קרא ראשון שלשה השני קורא שנים מפרשה זו ואחד מפרשה אחרת ויש אומרים שלשה לפי שאין מתחילין בפרשה פחות משלשה פסוקים
The Gemara raises an objection to the opinions of Rav and Shmuel from the following baraita: Two people may read a paragraph of six verses, but a paragraph of five verses may be read only by a single reader. If the first one read three verses, the second one reads the remaining two verses from this paragraph and then one verse from another, i.e., the following, paragraph. And some say that it does not suffice to read one verse from the next paragraph; rather, he must read three verses, as one may not begin a new paragraph and read fewer than three verses from it.
ואם איתא למאן דאמר דולג נדלוג ולמאן דאמר פוסק נפסוק
And if it is so, if it is permissible to do as Rav and Shmuel suggested, according to the one who said that the second reader repeats a verse that the previous reader recited, i.e., Rav, let him repeat the verse in this case as well. And according to the one who said that the second reader divides the verse, i.e., Shmuel, let him divide the verse in this case as well.
שאני התם דאפשר בהכי
The Gemara answers: There, in the case of the baraita, it is different, as it is possible to solve the problem in this manner by reading additional verses. On the New Moon, however, the next paragraph deals with an entirely different subject, and consequently it cannot be included in the Torah reading. Therefore, Rav and Shmuel presented alternate solutions.
If we can’t add pesukim to the New Moon reading because it is a permanent reading and the next paragraph isn’t relevant, would Monday and Thursdays readings have the same rule nowadays, that the readings are permanent (as opposed to the amoraic era, where there were no set weekday readings (Megillah daf 21B Rashi DH Rishon)) and the next paragraph isn’t necessarily relevant?