RoP:TI p.114 Summoning has:
Summoning is the Art of drawing a spirit into the infernalist’s presence, transporting it to him so that he may bargain with it or further target it with his Powers.
The sorcerer may summon any incorporeal creature with Might using this Art,
and may also affect incorporeal beings who have temporarily taken a physical
form through some variation of possession, though he does not summon the
body when he does so. The exception to this is demons, which have corporeal
bodies made of pure spirit, and so can be summoned with this Art.
Theurgy does not summon a Daimon proper, but invokes an aspect of that Daimon. See TMRE p.137 Daimons:
Daimonic spirits are powerful and unique beings, and the storyguide should
craft them to allow for the telling of interesting stories. The following examples
may act as useful models for designing your own Daimonic entities. <...>
A Daimon also does not respond in person — it sends an Aspect of its spirit.
The Aspect behaves as an independent earthly spirit while it is active, but when
its reason for existence ends, it is absorbed back into the Daimon, residing among the stars, so the Daimon knows what all its Aspects have done. However, binding or destroying an Aspect has no effect on the Daimon itself. The ability of Daimons to create multiple Aspects in different places permits more than one magus to enter into a pact with a single Daimon. Other spirits in general lack the ability to create multiple Aspects.
RoP:TI Goetic Summoning would attempt to draw a Daimon proper into the infernalist's presence. A TMRE Daimon has not even stats for this - so a SG will have to house rule/handwave a lot about them. But I think that this is not even necessary.
Let's continue with TMRE p.80f Invoke the Pact of (Daimon):
.A maga cannot bind an Aspect — it will just fade away, discarded by the parent spirit; she can only bind the Daimon itself if she can find the core spirit in the realm where it resides.
Goetic Summoning would hence have to summon the core spirit of the Daimon from its realm.
Whether Synthemata Magia can help there is most dubious.
See for this first RoP:M p.110 box Arcane Connections, True Names, and Synthemata. Then look up TMRE p.87f Synthemata Magia — Major Supernatural Mystery Ability to verify, that a wizard needs to be in the presence of the spirit to Intuit Synthemata, or have been in its presence if Researching Synthemata: both won't happen with the core spirit of a Daimon - and Synthemata Magia has no other methods to find Synthemata. So it doesn't help in getting the core spirit's Synthemata.