This beings aren't 5D in that sense, just being born in any higher dimension doesn't mean anything w/o proof of it applying mathematically like we use it.
They are stated to be fifth-dimensional, so not coming from the 5th dimension. So they do in fact have 5 dimensions (which is one of the reasons 3D beings cannot perceive their true form and they appear as varying beings and objects to everyone), we just don’t treat having 5 dimensions as being inherently superior to having 3 dimensions.
From the
tiering system FAQ:
“
Are higher-dimensional beings infinitely stronger than lower-dimensional equivalents?
Unintuitive as that may be: Not necessarily, as a number of characteristics through which we quantify the strength or power of a character can remain unchanged when transitioning between higher and lower dimensions. For example: Mass is a quantity that is detached from the dimension of the object which it is inherent to, and unlike volume is not divided in units corresponding to each particular dimension (1-volume [length], 2-volume [area], 3-volume, 4-volume...). It is singular in nature and its units equally apply to
all dimensions; whether it is distributed over an area or a volume only tells us about the span of space in which it is spread, not about the quantity itself.
…
Hence, a higher-dimensional entity can be both stronger or weaker than a lower-dimensional one, and thus, they are usually quantified based on their own feats, instead of dimensionality alone. If a character is merely stated to be higher-dimensional and simultaneously has no other feats to derive anything noteworthy from, then they are put at
Unknown, and the same applies to lower dimensions as well.
Do note, however, that them not qualifying for Tier 2 and above doesn't mean they are "fake" higher-dimensional beings or anything of the sort. It is simply that being higher-dimensional does not inherently mean they have infinite power in the first place, as explained above.
Also it is implied that the Contumelia could stop Maltruant’s Annihilaargh so them having higher-dimensional power is a possibility, take that as you will.