earliest time to apply together with my family

Hi guys

Hope someone can help here.
I got first T2 general visa on Aug 25,2013, and landed UK on Sep 7,2013.
My wife and my son got the first T2 general dependant visa on the same day(Aug 25,2013), However, they arrived in UK 3 months later(Dec 7,2013).

I asked solicitor(from famouse law firm with more than 10 years experience) who helped my T2 visa, solicitor told me my family and I both are qualified from July 29 even my wife and son arrived 3 months later. This makes sense to me as if I read the qualifying period includes "after visa granted before landing"

However, some advisors and some posts in the form said that we cannot apply together. My wife and son needs to wait 3 months.

I am a bit confused.

Can anyone help with my questions? If what solicitor said is true, whether solicitor needs to put additional cover letter to support that?

In the latest 5 years continuous version:
https://assets.publishing.service.gov.u ... .0-EXT.pdf

It has below:
PBS dependants
You must not include any absence from the UK during periods of leave granted
under the Rules in place before 11 January 2018 towards the 180 days allowable
absences.

Does that means I and my family can apply together after I got qualified even my family landed 3 months later?
Could someone confirm?
Thanks a lot.

Guys, I just called UKVI, and confirmed if my visa and my family's visa got approved at the same time, even my family arrived 3 months later, they can apply the same time with me as they accomplished with 180 days.

If someone had another real case which it's not the same, please help to share with us.