Yes. Gaining a dot in a Discipline lets you pick any one power of that level or below.
As Theik's answer points out, putting more dots into a Discipline lets you pick from any of the powers of that level or below. This is explicitly pointed out in the general rules for Disciplines on p. 244 of the V5 corebook (under "Selecting Powers"), as well as the example that follows it:
Every time a character gains a dot in a Discipline they choose one power from among the listed, either from their new Discipline level or below. Vampire characters normally have an equal number of dots and powers in a Discipline - no more, no less.
EXAMPLE:
At character creation, Martha has gained two dots of Fortitude. With the first dot she can choose either of the level one powers, picking Resilience. At the second dot she can choose either Unswayable Mind (the second level 1 power) or Toughness, the level 2 power. She picks Unswayable [M]ind. When she later gains her third dot, she can pick either Toughness or any on the level three powers: Defy Bane or Fortify the Inner Façade.
This quoted text appears just above the house-rule on the page linked in the question. What the house-rule changes is not whether you can pick multiple powers of the same level in a Discipline (which you can), but rather whether you can learn more than 5 total powers in a Discipline.
As Theik notes, you can normally only choose one power for each dot you gain in a Discipline, and you can only gain up to 5 dots total in a Discipline - so normally, you could only gain a total of 5 powers in any given Discipline. Purchasing new levels of a Discipline also gets increasingly expensive regardless of the powers you pick; picking both 1st-level powers, the 2nd-level power, and both 3rd-level powers for Obfuscate costs exactly the same amount as picking one power of each level from 1-5.
However, the house-rule makes it so that you can effectively ignore these limitations. It gives characters the option to spend the equivalent amount of XP that it would take to purchase that dot, effectively gaining that dot a second time and thus being able to choose the other power they did not initially pick.
For example, in the example in the text, Martha gains 2 dots of Fortitude, picking the Resilience power for her first dot and the Unswayable Mind power with her second dot. Normally, the only way for her to then gain the Toughness power would be to pick it when she purchases a 3rd dot in Fortitude by spending 3 * 5 = 15 XP. However, this house-rule allows her to purchase it as if she were purchasing her 2nd dot of Fortitude for the first time, spending only 2 * 5 = 10 XP to pick a 2nd-level power.
Thus, the house-rule effectively makes it cheaper to gain new powers, and removes the limitation on how many total powers you can learn in a Discipline.
