The spell begins with a description of the size of the portal that opens:
You conjure a portal that links an unoccupied space that you can see within your reach to a precise location on a different plane of existence. The portal is a circular opening, which can make from 5 to 20 feet in diameter.
Then enter what happens when you summon a creature whose name is known:
When you cast this spell, you can say the name of a specific creature (a pseudonym, title or nickname does not work). If that creature is on a different plane than the one it is in, the The portal opens in the vicinity of the named creature and draws the creature through it. to the nearest unoccupied space on your side of the portal.
While it does not specifically indicate that the size of the portal matters, it makes sense that the size of the portal is a limiting factor in what can happen through it. You can not get a creature through a hole that does not fit.
But that's where the Exprimido rules can come into play. The compression rules very well and that a creature of Gargantuan (the largest size category) must be able to tighten in space by looking at the rules regarding the size categories of the creatures and the space they control. A Gargantuan can be squeezed in a space of 15×15 according to those rules, but for the creatures whose dimensions are in the list, it is not reasonable to consider that with respect to the size of the portal.
We can see the real dimensions of the creature with respect to the size of the portal, and we will use the Tarrasque as an example (MM, 286):
Biped spit, the tarrasque is fifty feet tall and seventy feet long, weighing hundreds of tons.
That's a creature big enough to fit into a 20-inch diameter hole.
While the sizes of the creatures are based more on the control areas, the compression rules use those sizes. It seems that there is RAW support for both Yes (the gigantic size can go through spaces of 20 & # 39;) and No (the general dimensions listed are much larger and does not make sense), and would leave it to a DM as to how They decide the size descriptions versus the size categories on their table to decide.