SIMPLE IRA Mid-Year SH 401(k) Under New Plan Sponsor

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I'd love the thinking of folks who are more well-versed in SIMPLEs.

Company A maintains a SIMPLE IRA in 2024 & 2025; several employees of Company A create their own Company B in 2025. Company A maintained a SIMPLE IRA (I'm not sure if the SIMPLE IRA is still active); Company B established a 06/01/25 effective date SH 401(k) Plan (short Plan Year). Company A & B have different EINS with no ownership crossover.

I understand that when an employer establishes a mid-year 401(k) Plan that the deferral limit is adjusted based on the # of days/365 of each arrangement. Because these are two unrelated employers, my thinking is that this does not apply to this scenario, so all EEs can contribute the total $23.5k between the two arrangements if they would like (a maximum of $16.5k being attributable to the SIMPLE IRA).

• Do you agree that the deferral limit for the Company B 401(k) Plan does not need to be pro-rated based on the number of days it was in existence vs. the SIMPLE IRA?
• Since catch-up contributions are separate to each Plan, can a 50+ participant who contributed $10k to the SIMPLE IRA under Company A defer an additional $24.5k to the Company B 401(k) Plan? ($6.5k SIMPLE deferrals, $3.5k SIMPLE catch-up, $17k 401(k) deferrals, $7.5k 401(k) catch-up)
• If the Company B employees are still employees of Company A and participating in the Company A SIMPLE IRA, does that matter? Or is it just a consideration in that both the non-catch up deferrals to each arrangement count towards their overall 402(g) limit?
• As I write this out, I imagine that a relevant consideration is whether Company B and Company A constitute an ASG. If they do, would their contributions be subject to the adjusted deferral limits based on the days/365 of each arrangement?