All of them use wood r4 as official kernel and have no time bomb. Heck do you even know what you talk about? The r4idsn.com card is an official wood card, r4isdhc.com.cn is an ace3ds rebrand etc
Actually I have already looked into the kernels of all the Wood R4 kernels we have at the moment. The R4 carts that are from r4isdhc.com are using a TTMENU/Wood mix, basically it is using Wood R4 but with TTMENU components (Official Wood does not use anything related to DSTT), the Official Wood R4 flashcarts are the ones from r4ids.cn, their Wood R4 is literally running off of the old but modified akmenu from Acekard RPG. I am basically saying WITHOUT Wood R4 most of the clones you mentioned would be garbage just like the R4i SDHC 3DS RTS or any others from that line of flashcarts.
I just downloaded all the latest kernels for the flashcarts from r4isdhc.com, they aren't using Wood R4 as an official kernel, they are using the crappy R4i kernel that the flashcarts from r4i-sdhc.com uses. Which means that the Wood kernels these carts can use are definitely not official, I already looked at the boot files for both the modded Wood R4 and Official Wood R4, both are vastly different. The modded one as I already mentioned above is using TTMENU components (because the R4i SDHC series is basically just a DSTT clone), which means the Wood R4 kernel they use was indeed modified. I also discovered a crap ton of unofficial Wood R4 kernels from a couple links specifically made just for R4 clones and some older/official flashcarts.
For proof here are the kernel download links SPECIFICALLY from www.r4isdhc.com
All of them use v3.9b:
I downloaded the kernels from r4isdhc.com.cn as well:
All of them use the same kernel:
I used a hex editor to look at the file system, sure enough you find this right at the beginning: "SRAM_V110...PASS", this is only on the R4i kernels, which means yet again this was modified to be another Wood kernel, it isn't using anything official. This may not have a time bomb though since it does use Wood R4 in general, that doesn't make it official though.