Looks like we may soon be getting more things to buy using samples and requisition slips. The Catalog Expansion has no cost, and buying it does nothing. The Upgrade Effect text must be null for Catalog Expansion, that field just shows the effect for whichever upgrade was previously selected.
Edit: It's been acknowledged on the official Discord, looks like it's unintended:
ALERT: ROGUE ITEM DETECTED. The Ministry of Truth has confirmation that a rogue item called the "catalog expansion" is temporarily visible in the Ship Management menu and, in accordance with regulations, we instruct all Helldivers to avoid this rogue item until further notice. The Ministry of Truth cannot confirm the reliability or safety of this item, nor can they confirm its origin.
The mech can be really good for any mission type where you need to spend an extended period of time on an objective. Off the top of my head I'd say that includes civilian rescue (all variants except the 15-minute bot one) and geological survey, in addition to the eradication mission type you mentioned. You're going to spend a significant amount of time on the extraction / main survey site, with multiple patrols / dropships / breaches. You can get a lot of value out of a mech call-in during that time.
If it were up to me I'd change the mech strat to work like the orbital laser. Shorten the cooldown but cap the number of mechs you can deploy during a mission. The 10-minute cooldown feels overly punishing if you do the main objective shortly before extraction.
There already is a cap of 2 mechs per stratagem per mission.
I didn't even realize, that cooldown is so long I'd be hard-pressed to use it more than twice.