H1B COS approved despite a day's gap. Can I start working?

[needhelp2011]

Hi,
I'm currently in US on L2 and my H1 got approved with change of status. But I have a day's gap between 2 statuses. So my attorney advised me that the COS came as an error and that I should not start working till I get my Visa stamped and that 1 day gap will be counted as an illegal stay and will cause immigration problems later.
I called up USCIS toll free number and they said that I won't go out of status as an H1B approved person is allowed to enter US 10 days prior to Visa starting date(They asked me to verify H1B section under 8CFR). But my attorney says that that is applicable for people entering US and not for some one staying here. Which one I should rely on?
In the worst case if I'm going out of status for 1 day, how seriously it'll affect my green card application if I apply for one later?
Will this one day gap void my COS? Can I start working on H1B from oct 1?

Thanks in advance,

[kabkaba]

IMO, you can stop working on Sep 29 (or whatever the last day of I-94 is) and start wokring for the H1 employer on Oct 1.

[needhelp2011]

Thanks a lot for the reply. Can someone give me a more detailed answer ? also if its gonna be illegal stay how its gonna affect a green card application?

I'm not able to ignore either sides as its a well reputed attorney who told me that I should not work and its USCIS who told me that I can work. I'm so confused.