Front Mission 1st credits several TOSE staff under music and sound effects, but with the exception of Ryoue Takagi, all of them use fake names that appear to be plays on their actual names.

My attempts at decrypting them:
Hidenori Nagaoka = Hidenori Miyanaga
Fujio Kenji = Kengo Hagiwara (also on the DS remake, credited by real name)
Riyo Nishikida = Riyou Kinugasa (also on the DS remake, credited by real name)
Hiroshi Amajima = Hiroshi Nakajima (seems the most clear cut, I've linked this if that's okay)
Masaya Kandagawa = Masaya Tsunemoto

As a sidenote, it seems that Hidenori Iwasaki was widely falsely attributed as the arranger and composer of new tracks in the game for several years. Could be a misunderstanding based on the 4 + 1st boxset? Either way, the specific credits page for 1st actually credits no one for the arrangements or new compositions, so it seems Square Enix didn't want to give TOSE's composers the same sort of acknowledgment.

Very interesting. We have the same situation with the Final Fantasy I remake developed by Tose (originally for WonderSwan Color, then for PS1). Square never credited the actual composers/arrangers in the Final Fantasy I + II Original Soundtrack, leading people to think Nobuo Uematsu arranged the FFI WSC/PS1 soundtrack himself.

Tsuyoshi Sekito was credited for FFII WSC/PS1 because that game wasn't developed by Tose, but Kan Navi, they didn't have in-house composers.

TOSE was never credited to a SQEX soundtrack except some projects (like "World of Final Fantasy").

I think SQEX didn't credit them since there are ports of the original material, only the original composers should be credited(?), even there were third-party sound designers who compressed or arranged the music for the various platforms (And TOSE was known to be a "shadow-acting" developer back then, so maybe they were asked to not be credited at their client's discretion?).

Most of those who were involved in SQEX projects has since left the company, either joining SQEX or became freelance, and are still active with SQEX (like "Final Fantasy Record Keeper" or "Final Fantasy VII Rebirth").

Not sure which company properly credits TOSE in their soundtrack releases... (I think CAPCOM are the only one?)

I would imagine that they wanted to avoid drawing too much attention to Tose and their composers, so while they at least credited all the staff in game staff rolls, they excluded their names from OSTs. I've also noticed quite a few Tose staff later joining SQEX too, even Mitsuto Suzuki briefly worked at Tose in the mid 90s. Hiroshi Nakajima is a less common case of SQEX -> Tose.

And yeah, they were explicitly credited on the soundtrack for Ultimate Ghosts 'n Goblins, but no breakdown on who composed what - fairly typical for Capcom soundtracks of that era, sadly.

Well, avoiding RE0 status (which is complicated to know who is/are the true artist(s), following Kobuchi's comments and liner notes from Best Sound Box), "Revelations" series and "The Mercenaries 3D" have proper credits to TOSE (well, actually Kohmoto only).

For the rest, I think it's like other companies, where it's ambiguous.

Knowing Square, a company that for a long time bragged about making everything on their own, I tend to believe they were not very enthusiastic about crediting outsourcing companies, even more the people working at these companies. Hence the WSC and PS1 remakes of FFI only mentioning "Translation: TOSE CO.,LTD." in the credits... Fortunately, this has changed over the years.

But this is pure supposition, there might be other reasons.

This one in particular is peculiar because of them going a step further and obfuscating the names of the outsourced staff. But yeah, seems they wanted to release more ports and weren't willing to allocate the resources to develop those in-house, so just quietly outsourced them.

Maybe we should ask Hiroyuki Miura (producer of most ports) about this?