I don't think there's any canon source that touches on the interaction between svirfneblin and gloaming. On Arelith though, I've often found my svirfneblin characters making fast friends with gloamings. They have a few major details in common: a history of being tormented by drow, valuing freedom, and along with Deep Imaskari, being the only playable races in the UD that don't lean strongly evil. They're fun for svirfneblin to connect with, confide in, and develop alongside.
Often, a gloaming and svirfneblin will follow similar courses in Andunor, assuming they're played as a fairly typical member of their respective race. They'll inevitably fail to fit in with, or violently clash, with Andunor. It's a city with many drow and many slaves. Yes I know it's a 'trade' city not a 'drow' city, but drow NPCs are everywhere in Andunor and drow houses are the entrenched masters of two city districts. Even putting aside the fact that they're one of the most popular races on the server, the setting suggests they're a major force in Andunor.
The svirfneblin character can easily move on from this, given the existence of the Grotto, the lack of magical sunlight sensitivity, and the fact that they're generally welcome these days in surface settlements. A svirfneblin can still roleplay in the Underdark in relatively cloistered locations under Brogendenstein's protection. These days svirfneblin can start in the Grotto anyway and thus avoid the awkwardness of living with the three races who make a habit of hunting them down, torturing them, enslaving them.
A gloaming can't really do that. Outside of maybe the Ogre Trade Post, there's not an avenue for non-svirf Underdark characters to comfortably exist in opposition to Andunor. So good/neutral gloaming generally wind up on the surface, despite the vulnerability. I don't personally see a problem with this if they're respecting the vulnerability and not running around at day. It makes sense to me that a non-evil gloaming would rather be forced stay indoors for about 7-12 hours than live in a city of drow and slavers. I don't find it disrespectful of the setting or unrealistic. Many gloaming would probably see it as an overall much better life.
My Grotto-based svirfneblin has encouraged trusted gloaming to settle in Brogendenstein before, but it's always a bit of a lukewarm offer when they wouldn't actually be able to open the elevator to the Underdark on their own. Arelith svirfneblin have lived in harmony with the earthkin for I think about a century now and allowed them freely in their homes. I don't think extending the same to gloaming (maybe with the restriction that they be Brogendenstein citizens) would be outlandish and would fit quite well with server lore.
Overall I understand the plight of the 'surface' gloaming as they're not an especially fitting race for Andunor. I've had largely positive interactions with gloaming characters. Many become reliable allies against evil forces in the Underdark and my svirfneblin character in the government would cheerily write them Grotto passes if such a mechanic existed.